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TEXTILE CHEMISTRY 


TEXTILE CHEMISTRY 


AN INTRODUCTION TO THE CHEMISTRY 
OF THE COTTON INDUSTRY 


BY 
F. J. COOPER 
OF THE TECHNICAL COLLEGE, BLACKBURN 


J 0 ¢ ) 2 ) 
- oO 4 = ; - ; - : = = by : ? - 26 e i : , , 
) >» o < ) @ 93003 @ 0 ) oa oD 3 3 ? 
WITH 240 DIAGRAMS 
ry = 


NEW YORK 
E. P. DUTTON AND COMPANY 
PUBLISHERS 


PREFACE 


DVANCED manuals on various branches of the textile indus- 
As are fairly numerous, but often the proper appreciation of 

them is considerably impaired by a lack of elementary 
chemical knowledge on the part of students and workers who are most 
interested in their contents. 

This book is intended to supply this deficiency. 

For several years the matter incorporated in this volume has been 
the basis of instruction introductory to the systematic study of the 
technical processes of Sizing, Bleaching, Dyeing and Finishing, and 
the Chemistry of Mill Stores and Materials. It has been put into 
permanent form only after considerable experiment and experience. 

The Syllabus of the Union of Lancashire and Cheshire Institutes 
in Textile Chemistry is admittedly framed on it and the ground covered 
includes the subjects of the Syllabus of the City and Guilds of London 
Institute in “‘ Chemistry as Applied to the Cotton Industry,” Subject 
-28E in the programme of the Department of Technology ; it is hoped, 
therefore, that the book will be particularly suitable for classes in 
Technical Schools conducted under the regulations of these bodies. 

But it should appeal also to the young studious cotton operative 
who desires to increase his technical knowledge, and to those in posi- 
tions of authority in mills who wish to know something of the nature, 
preparation, and properties of the materials used in the various pro- 
cesses through which cotton must pass in its journey from fibre to 
marketable cloth. 

The attempt has been made—it is hoped successfully—to produce 
a manual which shall serve not only as a textbook for a school course 
which includes lectures and practical work, but also as a complete 
laboratory manual for those who cannot obtain special practical 
instruction, and finally as a trustworthy guide for the private student. 

The user hardly needs to be reminded that it should be worked 
through in an experimental manner; every exercise should be per- 
formed by, or demonstrated to, the student, and no attempt should 
be made to “cram up” the information it contains. 

Several friends have been good enough to read and criticize the 
manuscript when ready for the press, of whom I wish to thank 


CT a 


vi TEXTILE CHEMISTRY 


publicly Mr. Harold Hunter, of the Battersea Polytechnic ; Mr. H. G. 
Leigh, of this College; and Mr. R. B. Duerden, of Nelson. 

Many pieces of apparatus described in this book are new and 
original and not included in the usual trade catalogues of makers of 
Scientific Apparatus, but arrangements have been made with 


Messrs. Batrp & Tatnock, LTD., 
34, Gr. Ducitrn STREET, 
MANCHESTER, 


to supply the same, and all communications relating thereto should 
be addressed to them and not to the publishers or author. 

Small cotton hanks and dyes for experimental purposes may be 
obtained from 


Messrs. ‘‘ COMMERCIAL LABORATORIES,” 
Hart CHAMBERS, VICTORIA STREET, 
BLACKBURN. 


Finally, I desire to express my gratitude.to Dr. R. H. Pickard, 
F.R.8., for the opportunities he gave me, when he was Principal 
here, of developing this scheme of work in the day classes, and for the 
interest he took in it to make it successful. 


F. J. COOPER 


BLACKBURN, LANCGs, 


SECTION 


I 


II 


III 


IV 


VI 


Vil 


VIII 


CONTENTS 


PAGE 
CHEMICAL DIAGRAMS. CHEMICAL TooLs and how to use 
them. Balances; Bunsen Burner; Thermometers ; 
Hydrometers 1 
Guass MANIPULATION ; Cork-boring; Fitting up Simple 
Pieces of Apparatus : , ‘ ‘ : 15 


StmpLE Processes. Solution, Evaporation, Distillation, 
Crystallization, Filtration, Boiling, Melting. Deter- 
mination of Melting-points and Specific Gravities. 
Effects of Heat ; Ignition. Determination of Moisture 
and Ash : ; : 


CLASSIFICATION OF Matter. Identification of Common 
Substances. Physical and Chemical Changes 


WatTER. Chemical and Physical Properties; Tests for 
Purity ; Hard and Soft Waters ; Suitability for Trade 
and Domestic Purposes. Simple Water Analysis 


GaAsEs. General Characteristics ; Laws of Boyle, Charles. 
Diffusion. Identification of Gases. ArrR—Physical and 
Chemical Properties ; Chief Constituents ; aes ; 
Impurities ; Principles of Ventilation 


OxyYGEN; Oxidation and Reduction ; Oxides ; Lavoisier’s 
Theory of Combustion 


Acrps, ALKALIS, Basss, Satts. Indicators. Preparation 
and Properties of SunPpHURIC, Nitric, and HyprRo- 
CHLORIC Acids, and AMMONIA. ; : : 4 


Vii 


20 


34 


40 


47 


61 


66 


Vili TEXTILE CHEMISTRY 


SECTION 


IX Tue ELemMents or Coemicat THEeory. Atomic Theory ; 
Atomic and Molecular Weights; Laws of Chemical 
Combination; Equivalents and their Determination ; 
Valency. Symbols, Formule, Equations; Simple 
Chemical Arithmetic : : ; j : 


X Carson. Destructive Distillation of Wood and Coal; 
Carbon Dioxide ; Carbon Monoxide ; Water Gas ; Marsh 
Gas; Benzol; Hydrocarbons; Alcohols; Aldehyde ; 
Acetic Acid; Carbohydrates—Sugar, Starch, Cellulose 


XI CHLORINE, Preparation and Properties; Hypochlorites. 
Sulphur Dioxide ; Hydrogen Peroxide; Ozone . 


XII Aluminium, Zinc, Magnesium, and their chief Salts. Sul- 


phur and some of its Compounds. Analysis of a Simple 
Salt 


APPLICATION OF CHEMISTRY TO TEXTILES 


XIII Tue Natura Fisres. Use of the Microscope for Exam- 
ination of Fibres; Effect of Heat, Acids, and Alkalis 
on Cotton, Wool, and Silk Fibres ; Chemical Tests for 
Identification of Fibres; Determination of Moisture, 
Ash, Cellulose, etc., in Samples of Raw Me and 
Moisture and Ash in Wool and Silk 


XIV THE MaAcHIneERY. Examination of Coal for Moisture, Ash, 
and Calorific Value. Lewis Thompson and Roland 
Wild Calorimeters. The Testing of Flue Gases for Oxy- 
gen, Carbon Dioxide, and Carbon Monoxide. The Testing 
of Boiler-feed Water. Boiler Compositions. Classi- 
fication and Properties of Oils; Mineral Oils, Fatty 
Oils, Lubricating Oils. Determination of Viscosity, 
Flash-point, Bye weniger and bint 3s 
Matter 


XV Sizinc. EHlementary Study of the Chief Substances used 
in Sizing Cotton Yarn, e.g. Starches, Softeners, Soaps, 
Weighting Materials, Metallic Chlorides. Determina- 
tion of Ash, Moisture, Gluten, Fatty Acid, etc., in 
various Sizing Ingredients, and the Detection of Com- 
mon Impurities. Fermentation, Mildew, and Function 
of Antiseptics. Testing of Size ‘‘ Residues ” 


PAGE 


80 


101 


125 


139 


158 


168 


183 


CONTENTS 


SECTION 


XVI BriEacumne. Nature of Colour, Function of Detergents; 
Chief Bleaching Agents. Principles of, and Processes 
for Bleaching Cotton ‘ ; ‘ i 


XVII Dyertne. The Chief Methods adopted for Dyeing Yarn on 
an Experimental Scale with Substantive, Basic, Sulphur 
and Mineral Colours. Testing dyed Samples for Fast- 
ness to Light, Washing, etc. . ‘ , ¢ ; 


XVIII Mercerizina. Process of, and Detection of Mercerized 
Cotton : 


INDEX 


ix 


PAGE 


205 


214 


227 


229 


tah 


TEXTILE CHEMISTRY 


SECTION I 


I. HOW TO DRAW DIAGRAMS 


q oe correct representation of chemical apparatus is a very 
important preliminary to the study of chemistry. Very few 
lessons are complete unless accompanied by sketches or 

diagrams of the articles used in the various preparations. 

In order to reduce to a minimum the time spent in drawing dia- 


THE UNIT 
Fig 1 


grams, and to ensure that they shall be fairly uniform, some system 
should be adopted. The following method will be found to be as 
satisfactory as any, and more so than most. 


2 1 


2 TEXTILE CHEMISTRY 


All lines should be drawn first in pencil (where necessary with the 
aid of a ruler), and then the completed diagram inked in freehand 
throughout. Every diagram in this book has been produced in this 
manner. ; 

Circles should be drawn by tracing round a halfpenny (Fig. 1), and 
the diameter of this circle should be considered as a unit of length 
upon which is based the dimensions of the figures. 


The flask is drawn, as shown in Fig. 2, by making the circle, drawing 
a vertical diameter, and continuing it one unit. Parallel lines are 
drawn on each side of this, the width between being equal to } of the © 
unit length. Shoulders are put on where they meet the circle, the — 


CHEMICAL DIAGRAMS 3 


bottom is formed by cutting a segment at the base, and the flange is 
formed by drawing short straight lines at right-angles. 

The method for drawing a retort is shown in Fig. 3. 

The triangular flask is evolved from an equilateral triangle of sides 
14 units long (Fig. 4). 

Corks should be drawn with lines which are continuations of the 
neck of the flask, etc. (Fig. 5). Figs. 6 and 7 show (much enlarged) 
how holes should be represented in diagrams of corks. 


4 TEXTILE CHEMISTRY 


Glass tubing and glass bends should be drawn as two parallel lines, 
the corners being rounded off, the outside one last, as shown in Figs. 
8, 9, 10. Fig. 11 gives the construction lines necessary for drawing 
the tubes in a laboratory wash bottle. 


The beaker (Fig. 12), gas jar (Fig. 13), test tube (Fig. 14), and tripod 
(Fig. 15) are all very easily drawn. 

Rectangles form the skeletons for the aspirator (Fig. 16), bell jar 
(Fig. 17), and Woulf bottle (Fig. 18). 


CHEMICAL DIAGRAMS 5 


Displace- 
- ment 
Collection 


Fig 19 


Durette 


Parallel lines form the basis upon which are constructed the 
following: gas jar collecting a gas by displacement, pipette, burette, 
Liebig condenser, and retort stand (Figs. 19 to 23). 

Fig. 24 illustrates the correct way to represent the bunsen burner. 

The arrangement when heating a crucible supported by a pipeclay 


6 TEXTILE CHEMISTRY 


triangle resting on a tripod is given in Fig. 25. The combination 
shown in Fig. 26 represents an evaporating dish placed on a sand bath 
being heated by a bunsen burner provided with a rose. 


Liebig Condenser 


Fig.26 Frade 


If a gas is being collected by displacement of water in a 
pneumatic trough, the diagram is drawn as shown in Fig. 27. A gas 


CHEMICAL DIAGRAMS 4 


jar is standing on a beehive shelf. Liquid is always represented 
as a continuous straight line for the surface, with dotted lines 
under it. 

Other diagrams frequently required are:—Wuriz or distillation 


Distillation 
Flask 


flask (Fig. 28), acid or thisile funnel (Fig. 29), drying tower (Fig. 30), 
U tube (Fig. 31), retort stand and clamp supporting boiling-tubes, 
etc. (Fig. 32). 

The method of construction of a potash bulb is shown in three stages 
in Fig. 33 (1, 2, 3). 


8 TEXTILE CHEMISTRY 


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II. CHEMICAL TOOLS 


Every trade has its tools. In chemistry we call them apparatus. 
Those described in the following pages are of very general use and 
necessary for the work which follows. 

1. The Balance. This is the most important piece of apparatus 
a chemist possesses ; without it he can do nothing: in fact chemistry 


(3) 


ftash Bulb 
Fiadd 


was not a science till its workers used a balance. 
Good and accurate balances are now easily obtainable. 
form of. student’s balance is shown in Fig. 34. 


Adjust. 


Screw 


CHEMICAL TOOLS 9 


A box of weights containing grams and fractions of a gram must 
always be provided for use with a balance. Figs. 35 and 38 show in 
section the usual shape of brass gram weights, which are arranged in 
a box as shown in plan in Fig. 36. Note that the 20’s and 2’s are 
duplicated. A groove is cut in front for the tweezers (Fig. 37) with 
which weights are always moved. 

Fractions of a gram are often kept in a separate box or a separate 
compartment. They are usually numbered in milligrams and range 
from 500 to 10. 


F1¢.37 


SSS 


SSS 


SSS 


Fig. 36 


They are made of platinum, German silver, or aluminium in the 
form of foil (Fig. 39) or wire bent into various shapes. Fig. 40 is a 
new and very good form in which the wire is so bent that the weight 
in milligrams is seen at a glance. 

If it is required to weigh more accurately than to 10 mg. a rider is 
used on the beam. This article (Fig. 41) is a stirrup of aluminium 
wire which weighs exactly 10 mg., and if placed in the pan of the 
balance acts as a weight of 10 mg. But if it be placed on the beam 
it only weighs that amount if placed at the end. 

If the beam be divided into 10 equal spaces between the knife- 


10 TEXTILE CHEMISTRY 


edge and the pan, as in Fig. 42, and the rider is placed on one of these 
divisions, it will weigh less thanl0 mg. If on division 1, it will weigh 
I mg.; on division 2, 2 mg.; on division 3, 3 mg., etc. 


THE PRocESS OF WEIGHING WITH A BALANCE 


1. Test the balance to see if it is accurate—that is so when the 
pointer swings an equal distance on each side of the zero mark. 

2. Substances must always be placed on a watch glass or other 
receptacle—never on the bare pan. 

3. Weights should be placed on the right-hand pan. Commence 
with the largest ; remove it if it is too heavy, allow it to remain if too 
light ; and add in descending order, missing none. 


ig 41 

4. Do not put anything on or remove anything from the pans 
whilst the balance is swinging—always bring it to rest first. 

5. When a correct balance is obtained count up, first the number 
of whole grams, then the number of milligrams, and write down with 
a decimal point between, e.g. 25 grams 830 mg. = 25-830 grams. 

If the mg. had amounted to 83 only, a cipher would have been 
entered in the hundred column, e.g. 25-083. 


EXERCISES 


1. Find the weight of a crucible and lid. 

2. Weigh a beaker or an evaporating dish. 

3. Perform a “ difference weighing,” i.e. :— 

Weigh a tube containing some sand, empty some out, and reweigh 
the tube. Calculate how much sand was removed. 


CHEMICAL TOOLS Il 


4. Check the accuracy of exercise 3 by first weighing a watch 
glass alone, adding the expelled sand, and weighing again. 

Borda devised a method for correctly weighing a substance on an 
incorrect balance. ‘The substance is put on one pan of the balance, 
and a counterpoise on the other. This counterpoise is made of a pill- 
box and shot and sand. - Shot is added to the empty pill-box one at a 
time until just too heavy ; the last shot is then taken out, and grains 
of sand added a few at a time, until the pointer 
of the balance is at zero on the scale. 

The substance is now removed from the pan and 
weights are put in its place until the counterpoise 
is properly balanced. ‘Then this weight is the same 
as that of the original substance. 

2. The Joly Balance. This instrument con- 
sists of a delicate spring suspended from a sup- 
port. At the end of the spring hangs a pointer 
and a pan; and when required, a glass bob (Fig. 
43). 

The pointer moves in front of a scale attached 
to which is a mirror so that its position can be 
correctly read. 

From Hooke’s law we know that the elongation 
of the spring is (within limits) proportional to 
the stretching force. Therefore if a substance is 
put on the pan, and the reading taken, the sub- 
stance removed from the pan, and weights added 
until the same reading is obtained, the weight of 
the substance is thereby obtained. When taking 
a reading, the pointer should exactly hide its own F; 4 
image in the mirror. te ‘4 


JORODOO OO VED 


EXERCISES 


1. Find the elongation of the spring for a load 
of 1 gram. 

2. Find the elongation produced by adding 
the glass float, and hence calculate its weight. 

3. Weigh a watch glass with it and compare result with that 
obtained with an ordinary balance. 

4. Find the apparent loss in weight when the glass float is weighed 
in water and—if possible—other liquids, e.g. alcohol, sulphuric acid, 
glycerine, ammonia solution, zinc chloride solution. 

3. The Bunsen Burner. The heating apparatus for general use 
in the laboratory is the bunsen burner (Fig. 44), which is capable of 
giving two distinct flames, known as the luminous and non-luminous 


12 TEXTILE CHEMISTRY 


according to whether the air-hole at the base is closed or open. For 
ordinary purposes the non-luminous flame is used. 

The figure shows the correct method of heating ; the hot blue zone 
of the flame should just reach the bottom of the substance to be 
heated. 

4. Thermometers are used for registering temperature. A good 
thermometer is a necessity ; ordinary boxwood and paper-backed 
patterns are of no use for scientific work. 

They must be treated very carefully. The instruments are gradu- 
ated in degrees Fahrenheit or Centigrade, the latter being generally 
used by scientists. As a rule the degrees are numbered at each 10 


Figd4 


(Fig. 45), one figure being on each side of the graduation mark. The 
5 line is longer than the others. 

The relationship between the degree Fah. and the degree Cent. is 
shown in Fig. 46, from which it can be seen that a degree Fah. is $ of 
a degree C. 

5. Hydrometers are old-fashioned, inaccurate, and non-scientific 
pieces of apparatus; there are several modifications and empirical 
scales. They are however still frequently used in trade, although it 
is time they gave place to better apparatus. 

Their construction is based on the principle of buoyancy or flota- 
tion. Ifa solid, heavier at one end than the other, and lighter on the 
whole than a liquid, be placed in that liquid, it will tend to float in 
the liquid so that the heavier end is underneath (Fig. 47). 


CHEMICAL TOOLS 13 


The heavier this end is made, the deeper the solid sinks in the liquid ; 
and the denser the liquid, the higher a given solid floats in it. 

A body of this kind, when made in a long thin form, is called a 
hydrometer (Fig. 48). In the top part is a paper scale of degrees, 
which are quite empirical. Scientific data for relative densities are 
always given as Specific Gravity—not in degrees. 

Rule to convert degrees 7'waddell to sp. gr. Multiply by 5, add 
1,000, divide the number thus obtained by 1,000. 

E.g. convert 38° Tw. to sp. gr. 


Sp. gr. 1-19. 


To convert sp. grs., reverse the process, ie. multiply by 1,000, 
subtract 1,000, then divide by 5. 
E.g. convert a sp. gr. of 1-76 to ° Tw. 


14 TEXTILE CHEMISTRY 


Beaume’s Hydrometer Scales. 
(a) Lighter than water. 


144 Say ee 
Sp. gr. = Bo 134 and ° B. = anaes 134. 


.(b) Heavier than water. 


144 ie 144 
° = B. = —_ —, 
Peoes 144— B. ane Ate Sp. gr. 
Note.—‘‘ Twaddell”’ hydrometers cannot be used for liquids lighter 
than water. Of the many distinct Beaume scales, the above are the 


two best known. 


SECTION II 


I. GLASS MANIPULATION 


(a) O cut glass tubing. Place the tube flat on the bench, 
make one cut with a triangular file ; take in both hands 
(Fig. 49), the nick in front, and give a “ pull bend.” 
(6) To bend glass tubing. Heat in the yellow portion of a bat’s- 
wing or fish-tail flame (Fig. 50), holding the tube with both hands, 
gently rotating it all the time. The elbows should rest on the bench 
and the hand be held as shown in Fig. 51, which is a side view. When 
the glass is quite soft it should be removed from the flame and bent 
into the required shape, and held fast until it sets. 


Fig. 52 shows the appearance of good glass bends. Fig. 53 shows 
faulty ones, due to overheating, careless bending, using wrong flame, 
etc. 


15 


16 TEXTILE CHEMISTRY 


As an exercise make bends of the shape and dimensions given in 
Fig. 54 A to F. 

(c) To smooth glass ends. Use the non-luminous flame ; hold as 
shown in Fig. 55, rotating all the time, till the glass just melts. 


(d) To make a jet. Heat tube in a bunsen flame, remove, draw 
out in both directions. Cut off as shown by the dotted lines (Fig. 56), 
and smooth both ends. 

(e) To make a closed tube or bulb tube. (. 

First make a jet, then close the end by \ 
holding it in the bunsen flame (Fig. 55). Vs 
Gently blow down the open end, holding 
the tube vertical (Fig. 57). If the tube is 
to be closed only, and no bulb blown on it, \ ( 
the thickness should be uniform, neither sharp \ 

or ‘‘ blobbed ” (Fig. 58). 


ee 
Fig 561 Fig 57 


Note.——Always allow hot glass to cool on an asbestos mat, and 
smooth all cut ends. 


II. CORK-BORING 


Select a cork slightly too large for tube, flask, etc., and roll it with 
gentle pressure under the foot to make it soft. Select a cork-borer — 
slightly smaller than the tubing being used. 

Hold the cork in the left hand, cork-borer in the right (Fig. 59), and 
bore with a screw motion, without excessive pushing. Get nearly 
through and then place the cork against a hard surface to finish, in 


GLASS MANIPULATION 17 


order to obtain a clean cut. Withdraw the borer by screwing in the 
reverse direction. 

Fig. 60 shows plan and section of corks bored with one and two 
holes respectively. The test for a well-bored cork is the appearance 
of the boring—removed by pushing out with a smaller borer. This 
should be a perfect cylinder. 


~~ =a = 


Tig 58 


Fig 59 


Practice on waste corks until proficiency is attained. 

To insert glass tubing in a cork, first wet the tube and then screw 
it in with both hands close together. If pushed or forced in, the glass 
will break and a serious cut may result. 


18 TEXTILE CHEMISTRY 


II. FITTING UP APPARATUS 

The following diagrams represent apparatus commonly used in 
laboratory practice, and the student is advised to set up each one in 
order to acquire manipulative dexterity. 


Fig 64 


Minsik 
L 


GLASS MANIPULATION 19 


Fig. 61 is of the laboratory wash bottle which contains distilled 
water. 


Fig. 62 is a simple melting-point apparatus that will be used later. 
Fig. 63 represents a test tube provided with a gas leading tube, 
clamped on a retort stand. The evolved gas is often collected over 


water. Fig. 64 shows how this is done in a pneumatic trough with 
a beehive shelf and gas jars. 

Fig. 65 is a diagram of a simple condensing arrangement for 
preparation of a small quantity of distilled water. 


SECTION III 


SIMPLE PROCESSES 
I. SOLUTION 


ATER is a solvent, i.e. a liquid which is capable of dis- 
solving substances. When a substance dissolves in a 

\ \ liquid, it disappears to sight as a separate substance— 
it may however impart a colour. The substance itself is said to be 
soluble in the solvent and the liquid thereby produced is called a 
solution. 

Water is not a universal solvent, but it will dissolve more sub- 
stances than any other known liquid. A few substances which are 
insoluble, i.e. not soluble in water, are silver chloride, barium sulphate, 
most fats and oils. Sulphonated oils, such as Turkey red oil, are 
soluble in water. 

Liquids which are soluble in other liquids are said to be miscible. 
Alcohol and glycerine are miscible with water; oils are not miscible 
with water as a general rule. 

Gases vary considerably with respect to their solubilities in 
water. The most soluble gases are ammonia, hydrochloric acid, sul- 
phur dioxide, sulphuretted hydrogen. The least soluble are hydrogen, 
oxygen, nitrogen, air, and carbon monoxide. 

The extreme solubility of ammonia in water can be illustrated by 
means of the apparatus shown in Figs. 66 and 67. 

As a rule the solubility of a solid substance is increased by heat- 
ing the liquid (an exception is lime). Gases are expelled from solution 
by boiling the liquid—some completely, some only partially, as with 
hydrochloric acid. 

Next to water the most important solvents are :— 

(2) Alcohol and Methylated Spirit, which dissolves shellac, 
iodine, fats, resins, camphor, etc. 

Solutions in alcohol are called tinctures. 

(6) Carbon disulphide, which dissolves sulphur, phosphorus, fats, 
and oils. 

(c) Ether—dissolves fats, iodine, india-rubber. 

(d) Chloroform—dissolves fats, gums, resins, iodine. 

20 


SIMPLE PROCESSES 21 


(e) Benzene—dissolves fats, rubber, and many organic substances. 

The dissolved solid can be recovered from solution by evaporating 
off the solvent, and the solvent can also be obtained if the product 
of evaporation be condensed—the process 
being known as distillation. The liquid 
which distils overis known as the distillate. 
Distillation may be used to prepare a com- 
pound—as nitric acid (q¢.v., page 72 et seq.), 
or to separate two mixed liquids, such as 
alcohol and water. 

The piece of apparatus in which the 
vapour is cooled is called a condenser. Fig. 


22, page 6 , shows a Liebig condenser, and . 

Fig. 68 the worm form. An arrangement i Dink 

for preparing large quantities of distilled +3 

water is shown in Fig. 69. . 2 
Solution sometimes raises the température (<eN = 


of the solvent, e.g. caustic soda in water. - 
Sometimes the temperature falls, e.g. when 

ammonium chloride is dissolved. Sometimes 

a soluble substance is mixed with an insoluble N \ 
one—solution can be used to separate them. 


II. SATURATED SOLUTION 


If equal quantities of water be mixed 
with gradually increasing quantities of salt, 
it will be found that ultimately a point is 
reached at which the water ceases to dissolve 
more salt. Similar results are obtained with 


22 TEXTILE CHEMISTRY 


other liquids and other solids. When this point is reached the 
solution is said to be saturated. 

But if a cold saturated solution be heated, more solid can be dis- 
solved, and if this hot solution be now cooled, the excess is deposited 
as crystals. 


III. CRYSTALS 

possess a definite geometric shape but have not a constant size. 
The size of the angles between the faces is one factor which helps to 
classify a crystal,.which may be defined as a regular solid of definite 
form enclosed by four or more faces. 

All crystals belong to one or other of seven systems which are dis- 
tinguished one from the other by the number of planes of symmetry, 
and the number and inclination of the axes it is possible to obtain 
from the specimen. A plane of symmetry is 
produced by cutting a crystal into two equal 
portions in such a way that one half is 
symmetrical in shape with the other (Fig. 70). 

Crystals exhibit a property known as cleav- 
age, i.e. a tendency to break more easily in one 
direction than another. Crystals may be ob- 
tained by various methods :— 

Fig (0 (1) Cooling after Fusion, e.g. prismatic 
sulphur, granite, and many metals. 

(2) Sublimation, e.g. iodine, white arsenic. 

(3) Solution and evaporation, e.g. sugar candy; salt. 

(4) Cooling a hot saturated solution (see Practical Exercises, 
page 24). | 


IV. PRACTICAL EXERCISES IN SOLUTION, ETC. 

(a) T'o determine whether a Solid is soluble or insoluble in Water or 
other Inguid. 

Test the solvent to see what residue it leaves on evaporation to 
dryness. 

1. Place the substance you are experimenting with in the bottom 
of a test tube, half fill with the solvent, place your thumb over the end 
and invert several times. 

2. If the solid has not disappeared, gently warm over a bunsen 
flame, and if necessary, boil. 

3. To say if the substance has dissolved. If it has disappeared 
there is no doubt it has dissolved. If some solid remains, the mixture 
must be filtered. 

4. Use apparatus as shown in Fig. 75, page 25. The liquid which 
passes through the paper into the beaker is called the filtrate. Note 


SIMPLE PROCESSES 23 


that it is clear; if not, pass it through again. The dissolved portion 
is now present in the filtrate. 

5. Evaporate this filtrate to dryness, using a porcelain basin on a 
sand bath. For more accurate work the apparatus shown in Fig. 71 
is used. 

6. If solid substance (other than that yielded by the evaporation 
of the solvent) be left in the basin the substance was soluble ; if not, 
it was insoluble. Sometimes it is desirable to weigh the basin before 
and after evaporation of the filtrate, sufficient information not being 
obtainable by inspection. 


EXERCISES 


Is sodium carbonate soluble in water? Is it soluble in dilute 
hydrochloric acid? Is sulphur soluble in water? Is tallow soluble 
in carbon disulphide ? Is soap soluble in alcohol? Is it soluble in 
ether ? 

Note——tThese last three solvents must not be brought near a 
flame. 

(b) To find of any Change in Weight occurs when a Solid dissolves in 
Water. 

Put a little water in a beaker, and a few crystals of ammonium 
chloride on a watch glass, and arrange as shown in diagram (Fig. 72). 
Weigh the set. Carefully tip the solid into the beaker, replace watch 
glass, and when the crystals have dissolved weigh the set again. 
What do you find ? 

(c) To prepare a cold saturated Solution of a Substance and to deter- 
mine the Amount of dissolved Substance in a given Volume of Solution, 


24 TEXTILE CHEMISTRY 


Also to find the number of parts of Solid dissolved in 100 parts of Water. 

A. To make the cold saturated solution (say of nitre). About one- 
third fill a boiling-tube with water, add a teaspoonful of nitre, and 
gently warm the liquid. When all the nitre is dissolved, cool under the 
tap. If crystals are deposited the solution is saturated. If not, more 
nitre must be added and the process repeated. 

B. To find the dissolved solid in 100 c.c. of solution. Weigh a 
clean dry basin, put in 20 c.c. of solution, measured with a pipette, 
evaporate to expel the water, and when dry and cool, reweigh. In- 
crease = amount of nitre in 20c.c. Calculate for 100 c.c. 

C. To find parts of solid in 100 parts of water. Weigh a dry basin, 
half fill with solution, and weigh again. Evaporate to dryness, weigh 
basin and residue. From these weighings find weight of water and 
weight of solid present. Calculate for 100 grams of water. 


How to record weighings— 
For Exercise B. For Exercise C. 
Basin + Residue Basin + Solution 


Il. ll 


Basin jonlyse ce a, he Basin only 
Nitre dissolved in Solution = 
SOSOIG) eae ae 
Se Basin + Residue. = 
Basin only = 
Solid . nae 


(d) Crystallization. To prepare Crystals of Nitre and Sal-ammoniac 
from Solution. 

Make a hot saturated solution of the salt. Pour into a watch glass 
to cool. If a thick deposit is formed, too much solid has been used. 
Add water and repeat. If it gets cold without forming crystals, add 


more solid and repeat. When crystals are formed slowly and per- 
fectly, make a sketch of them as shown in Figs. 73 and 74. 


SIMPLE PROCESSES 25 


(e) Preparation of Standard Solutions. 

Standard solutions are solutions which contain a known weight of 
the dissolved substance in a definite volume of the solution. The 
usual method adopted for preparing them is to weigh out the solid 
and then dissolve it in some of the solvent. The solution thus formed 
is transferred without loss to a measuring vessel, and more solvent 
added to make up the full volume required. The vessel is stoppered, 
the liquid thoroughly mixed, and finally transferred to a bottle which 
is suitably labelled. 


EXERCISE 


Prepare standard solutions containing 10 per cent. soda ash, 20 
per cent. Glauber salt, and 5 per cent. common salt. 

Also make a solution of the given dye stuff 
of such a strength that 1 c.c. of it contains -001 
grams of dye. 

Carefully label and preserve these standard 
solutions. 

(f) T'o separate the Constituents of a Mixture 
of soluble and wmsoluble Substances, and to deter- 
mine the Proportion of each present. 

Transfer the mixture to a weighing bottle 
or test tube fitted with a cork. Weigh and 
record as shown below. 

Empty some of the substance from the 
bottle into a beaker (or boiling-tube), and 
weigh bottle again. Enter weighing. : 

Add distilled water to the beaker in sufficient Fig oy 
quantity to dissolve all the soluble portion. 

Stir well and warm gently. When solution is considered to be com. 
plete, filter the liquid to separate the insoluble substance from the 
solution. 

When filtering, remember never to have the paper more than half 
full, and always to pour down a glass rod (Fig. 75). 

Transfer every particle of insoluble substance to the filter paper 
by washing down with water, or (if possible) use a camel-hair mop. 

Wash the substance on the filter paper, collect all washings, add 
to the original filtrate and evaporate to dryness in a weighed evapor- 
ating dish on a sand or, preferably, water bath or steam oven. Record 
weighing. 
Open out the filter paper, place it on another paper from the same 
packet, and dry in a steam oven. Use the bottom paper to obtain 
weight of filter paper only. 

Calculate in each case the percentage as shown on next page. 


26 TEXTILE CHEMISTRY 


MetTHoD OF RECORDING RESULTS 
1. To determine Weight of Mixture taken for use. 


Bottle + Substance at first 
» + Mixture left 


Mixture used 


| 
8 


2. Weight of soluble Substance present in Mixture used. 


Evaporating dish + Residue sa grams. 
be) 99 only seh 99 
Soluble substance = 


y 33 


3. Weight of insoluble Substance present in Mixture used. 


Filter paper + Residue grams. 


ll Il 


39 


Insoluble substance z 


4. To determine Percentage of each Portion. 
(a) The soluble portion. 
Multiply the weight of soluble substance by 100 and 
divide by weight of mixture used :— 


y X 100 
x 


(6) The insoluble portion. 
Multiply the weight of insoluble substance by 100 and 
divide by weight of mixture used :— 


z X 100 
z 

Suitable mixtures are alum and sand, nitre and sand, clay and 
soda ash. | 

As a further exercise find the proportions of the constituents in 

(1) a mixture of sand, salt, and chalk. 

(2) iF sulphur, nitre, and charcoal. 

Note.—Chalk is soluble with decomposition in dilute hydrochloric 
acid, and sulphur is soluble without decomposition in carbon disul- 
phide. 

(3) A mixture of chalk and clay. Find a suitable solvent by 
experiment with separate samples of chalk and clay. 


SIMPLE PROCESSES 27 


V. FILTRATION 


is the process employed for separating insoluble or suspended 
matter from aliquid. Onasmall scale, porous paper, cotton wool, or 
glass wool can be used, the porous substance being inserted in a piece 
of apparatus called a funnel. 

Sand, gravel, brick ends, wood wool, charcoal, canvas, porous 
porcelain, and spongy iron (ignited iron oxide) are all used on larger 
scales of filtration, such as for a town’s water supply, sugar-refining, 
water-softening, sewage treatment, etc. 

The rate of filtration depends upon several factors, e.g. 

(a) Density and nature of the precipitate or suspended matter, 
which may be :— 

1. Flocculent, as copper hydroxide. 

2. Crystalline, as lead chloride. 

3. Gelatinous, as aluminium hydroxide. 

4. Slight or turbid, as when silver chloride is precipitated from tap 
water. 

As a rule Nos. 1 and 3 take longer to filter than Nos. 2 and 4. 

(b) Temperature of the liquid. Other things being equal, a hot 
mixture filters much quicker than a cold one. 

(c) Pressure on the surface of the liquid as it passes through the 
filtering medium, illustrated in the filter or suction pump. 

(d) Porosity of the filtering medium. For this reason a filter paper 
is first wetted with clean water, so that the pores may not be partly 
filled up with the solid that is added first. 

After a mixture has been put on a filter paper and the liquid has 
filtered through, the solid requires washing to remove the rest of the 
liquid which has adhered to the solid or the paper. This is done by 
blowing on it a jet of water from the wash bottle (Fig. 61, page 17). 

Strong acids and caustic alkalies destroy paper ; they are therefore 
filtered through glass wool, which is made into a tuft and placed in the 
funnel. 


VI. BOILING AND MELTING 

A liquid is said to boil when it is in a state of active ebullition, i.e. 
bubbles are passing quite through its mass. ‘The process is not iden- 
tical with evaporation, and it is distinguished from it in several ways, 
€.g. -— 

Boiling takes place at a definite temperature only—evaporation 
can occur at any temperature. 

Boiling occurs through the whole body of the liquid—evaporation 
from the surface only. 3 

Boiling is apparent to the sense of sight, but evaporation is usually 
invisible. 


28 TEXTILE CHEMISTRY 


Continued boiling does not alter the temperature of the liquid (if 
pure) ; continued evaporation lowers the temperature. 

These differences can be illustrated by experiments, e.g. boiling 
water in which is placed a thermometer ; allowing alcohol and ether to 
evaporate on the palm of the hand; placing a dish of water in a cold 
room for several hours. 

The temperature at which a liquid changes to a gas, when the liquid 
is in a state of active ebullition, is called its boiling-point (written b.p.). 

Boiling-points are considerably affected by pressure. This pro- 
perty is made use of in the Papin digester (Fig. 76) and autoclaves, 
pieces of apparatus that are often employed in industrial chemistry. 

The reverse process is called condensation or liquefaction. 

A solid is said to melt or liquefy, or fuse, when it changes its state 
to the liquid condition. The melting-point (m.p.) is the temperature 
at which this change takes place. 

Solution must not be confused with 

: melting; e.g., in the general case sugar 

ci does not melt in water, it dissolves. 

Pressure as a general rule causes the 

melting-point to rise. This explains why 

granite and other rocks are solid inside 

the earth, although they are at very high ~ 
temperature. 

In the case of water, pressure lowers 


Joss \ the. m.p. Some solids have not been 


2S 
F; 6 liquefied yet, e.g. arsenic and carbon. 
ig (' The reverse of the process is termed 


solidification. The boiling-point or melt- 
ing-point of a substance is a very valuable aid in determining the 
purity of a chemical or commercial commodity, e.g. butter may be 
distinguished in many cases from margarine by finding the m.p. of 
the fatty acids in the samples. 


VII. PRACTICAL EXERCISES IN DETERMINATION OF 
MELTING-POINTS . 

Use the apparatus shown in Fig. 62, page 17 , and determine the 
m.p. of tallow as follows. Just melt some tallow in a small test tube ; 
dip the thermometer into it and remove at once. If this is done 
very rapidly a thin coating of fat will solidify on the bulb. Replace 
the coated thermometer in the boiling-tube and very slowly raise the 
temperature. Take the reading of the thermometer at the instant 
the melted fat drops from the bulb. 

For obtaining accurate results the fat should be allowed to set 
twenty-four hours in a cold place before the test is made. 


SIMPLE PROCESSES 29 
VIII. SPECIFIC GRAVITY AND ITS DETERMINATION 


By specific gravity is meant the number of times a substance is 
as heavy as the same volume of water. Suppose 20 c.c. of a sub- 
stance weigh 18-6 grams, and 20 c.c. of water weigh 20 grams, then 
the sp. gr. of the substance = 18-6 ~ 20 = -93. On the face of it, it 
appears therefore that sp. gr. should be easily and accurately deter- 
mined. In practice however it is often very diffi- 
cult to determine accurately the volume of the 
substance. 

The following methods are in general use :— 

Liquids. Approximate method. Counterpoise a 
dry beaker, weigh in it 50 c.c. ofa dilute solution of Specific 
caustic soda, measured by means of a pipette (Fig. Gravity 
20, page 5) or a measuring cylinder. Empty out, Dottle 
and weigh 50 c.c. of pure water. Calculate the sp. 
gr. of the solution of soda. Fi 

Accurate method. Carefully weigh the piece of ty ie / 
apparatus known as a specific-gravity bottle (Fig. 

77). Say when dry it weighed 12-34 grams. Fill it with the liquid 
whose sp. gr. if is required to determine (say a dilute solution of zinc 
chloride), and insert the stopper. 

The excess of liquid is expelled through the 
perforation. Carefully wipe the bottle dry, and 
reweigh, say = 72-63 gr. Then weight of this 
volume of liquid = 72:63 — 12:34 = 60-29 grams. 

Empty out the liquid, clean the bottle, and fill 
it in the same way with pure water. Wipe and 
weigh again, say = 62-21 grams. Then the weight 
of this volume of water = 62:21 — 12-34 = 49-87 
grams. 

Then, as the volumes are the same, the 

Sp. gr. = 60-29 + 49-87 = 1-21. 

Commercial method, using hydrometers (Fig. 
48, page 13). The method of using these instru- 
ments is given on pages 12-14. The liquid must be 
put in a gas jar about 14 inches wide, so that the 

: hydrometer can float freely. The reading is 

Fig /8 taken at the surface of the liquid (Fig. 78). 

As an exercise find the sp. gr. of glycerine, 
strong caustic soda solution, methylated spirit, concentrated sul- 
phuric acid, concentrated hydrochloric acid, ammonia solution, and 
pure distilled water. | 

Rapid accurate method. One of the quickest and most accurate 


30 TEXTILE CHEMISTRY 


methods of finding sp. grs. of liquids is by the use of the Joly balance 
(Fig. 43, page 11). Remove the pan of the balance and substitute the 
glass bob. ‘Take the reading of the pointer when the bob is floating 
in air—say graduation mark is 163. Partly fill a beaker or large test 
tube with water, bring it underneath the bob, and allow the latter to 
be freely and completely immersed. Take reading again, say = 147. 
Then the upward push of the water is represented by 163 — 147 = 16 
graduations. | 

Remove vessel of water, carefully wipe the bob, and repeat with 
the liquid whose sp. gr. it is required to find. 

Say reading is 149. Then upthrust of the liquid is represented by 


163 — 149 = 14 graduations. 
thrust of liquid 14 
Then Sp. gt. ee ee 
eee upthrust of water 16 : 


As an exercise use the same liquids as with hydrometers, and 
compare the results. 


Blow 


Liquid chemicals are often supplied to mills and works in carboys, 
drums, or similar vessels, e.g. strong acids, alkalies, zinc and mag- 
nesium chlorides, oils, etc. The safest and simplest method for 
removing samples for testing is to fit up an arrangement, similar to 
that adopted for the laboratory wash bottle (Fig. 61, page 17). A good 
and tight-fitting cork carrying two glass tubes should be inserted into 
the mouth of the carboy (Fig. 79). By blowing at the end of tube A, 
liquid is driven out through tube B and can be collected in vessel C. 

Solids. The best way to find sp. gr. of fats and waxes is to 
make very small pellets of them, and mix alcohol (either ethyl or methyl 
will do, but ordinary methylated spirit is not suitable, due to precipita- 
tion of gum) and water till the pellets will neither sink nor float in the 
mixture except under compulsion. Then find the sp. gr. of this liquid, 
which is identical with the sp. gr. of the solid. 


SIMPLE PROCESSES 31 


EXERCISE 
Find sp. gr. of tallow, spermaceti wax, and paraffin wax. 


IX. EFFECTS OF HEAT 


The general effect of heat upon a substance is to produce a change. 
Sometimes this change is physical, sometimes chemical, sometimes 
both (see Section IV). 

Under the head of physical there are :— 

(a) Alteration in volume, usually an increase. 

(6) Decrease in density. 

(c) Change in state, e.g. solid to liquid. 

Among chemical effects produced are found :— 

(a) Decomposition of compounds. 

(8) ‘The dehydration of substances containing moisture and water 
of crystallization. 

(vy) The formation of chemical compounds from constituent 
elements. 

(6) The decomposition of original compounds and formation of 
new ones. 

(e) The conversion of a mixture of substances into one or more 
compounds. 

The process of strongly heating a solid is often termed ignition— 
it is not identical with the ordinary use of the word. 


EXERCISES 


1. Heat mercuric oxide in a test tube. Test gas evolved with a 
glowing splint. 

2. Perform a similar experiment with potassium chlorate. 

3. Heat crystals of bluestone or copper sulphate. 

4. Heat magnesium ribbon in air. 

5. Heat wood in a test tube and note inflammable gas produced. 

6. Heat a mixture of iodine and mercury in a test tube. 


X. DETERMINATION OF PERCENTAGE OF WATER IN 
SUBSTANCES | 

Many raw materials and substances used in the textile industry 
contain water, the proportion of which it is often desirable to know, 
e.g. cotton yarn and cloth, starches, fats, soaps, ‘“ compositions,” 
solutions of caustic soda, zinc chloride, magnesium chloride, etc. 

If the substance is a solid it is weighed in a wide test tube or weigh- 
ing bottle (Fig. 80) or aluminium tray, or pair of watch glasses clipped 
together (Fig. 81), or glass evaporating-basin; and then put into a 
steam oven until there is no further loss in weight. The total loss 


32 TEXTILE CHEMISTRY 


represents moisture (and other constituents volatile at 100°C.). It 
is returned as a percentage. 

If the substance is a liquid, it should be put into a small test tube 
3in. X $in., made to stand upright by placing the end in a cork (Fig. 
82). The method of working is exactly the same as that for a solid. 


EXERCISES 
Find percentage of water in flour, farina, soap, caustic soda solution, 
zine chloride solution, magnesium chloride solution. 
XI. TO DETERMINE PERCENTAGE OF ASH 


The substance is first weighed in a crucible, then heated over the 
bunsen flame, at first gently, then strongly until a grey white residue is 


1; 


Shh 


Fig 80 


obtained. The crucible lid must be removed while the heating is in 
progress, and the flame must be arranged as shown in Fig. 44, page 12. 
The hot blue zone of the flame should just reach the bottom of the 
crucible. 

Many textile materials greatly increase in volume and sometimes 
froth on heating ; hence the crucible should never be more than one- 
third full ; and it is generally advisable to remove the burner for a few 
minutes at intervals. 

As a rule a black mass is obtained first. If it is hollow it should be 
broken gently when cold and made to fall to the bottom of the crucible. 
This blackness is due to the presence of carbon. The heating, which 
may now be intense, must be continued until all black is burnt away, 
as carbon is not ash. The whiter the residue obtained the better will 
be the result. 

Results should be tabulated in the following way :— 

Weight of crucible and lid + Substance = 
” 29 » only mG 


.. Amount of substance used = a gm. 


SIMPLE PROCESSES 33 
Weight of crucible and lid + Ash 


ll Il 


9? : 939 9? only 
*, Amount of ash = b gm. 
Then percentage ash BOX aa 
EXERCISES 


Determine the percentage of ash in powdered magnesite, flour, 
commercial glycerine, sago flour. . 

An exercise which combines a moisture and ash determination is 
one with China clay, to find percentage of “free ’’ and ‘‘ combined ” 
moisture. 

First dry some in a steam oven and find loss per cent. This is 
“free moisture.” | 

Next take this steam-dried clay, and heat over a bunsen burner as 
in ash determinations, until there is no further loss. This second loss 
gives the “ combined moisture.” 


Record results as follows :— 
Clay + crucible = 


eo only 
*. Clay = 538 (say) gm 
Crucible + Clay not dried = 
Bf e. eke ,, steam-dried = 
*, Free moisture = ‘1 = (say) gm 
Crucible + Clay steam-dried = 
a + ,, ignited a 
-, Combined moisture =  -613 (say) gm 
Percentage free = ae 1-86 per cent. 
5-38 
Percentage combined = oie et 11-4 per cent. 


5:38 


N.B.—Both results are calculated on the original weight of clay, 
i.e. 5:38 gm. 


3 


SECTION IV 


I. CLASSIFICATION OF MATTER 


HE word matier is used to include practically an infinite 
number of things—hence the need for classification. 
For physical purposes there are two classes: (1) Solids. 
(2) Fluids subdivided into liquids and gases. The chemist has 
adopted other classifications, some of which are not perfect—the classes 
overlap or are not inclusive. 

The most important chemical classification is the one which divides 
matter into (1) Elements, (2) Compounds, (3) Mixtures; and every 
known substance can be placed in one or other of these three classes. 

An Element is a thing which has not by any known means been 
resolved into anything simpler—it yields nothing but itself. Ninety 
substances are known which have not been split up. Some of the 
commonest are: carbon, iron, copper, sulphur, lead, silver, gold, 
oxygen, nitrogen, hydrogen, aluminium, phosphorus, mercury, iodine, 
sodium, potassium, chlorine, tin, magnesium, zinc. 

Elements are divided into two sub-classes: (a) Metals, (6) Non- 
metals. This however is not a perfect division, as there are some 
elements which seem to belong strictly to neither class. These are 
called metalloids. Arsenic is one example. 

Metals as a rule possess the following characteristic properties : 
(1) are malleable, (2) are ductile, (3) possess a peculiar lustre, (4) have 
a high specific gravity, (5) ring when struck, (6) are good conductors of 
heat and electricity. 

They also possess the property of intimately mixing with each other 
when melted together or compressed, to form alloys. Some common 
alloys are pewter, bronze, German silver, type metal, solder, fusible 
metal. 

Non-metals are elements which do not possess metallic properties, 
i.e. they are not malleable, not ductile, etc. This class includes all the 
elementary gases, and carbon, sulphur, phosphorus, and iodine. 

Compounds are things which contain two or more elements united 
together in certain definite proportions in the smallest piece of the 


34 


EE ———— 


CLASSIFICATION OF MATTER 35 


substance which is capable of having an existence as such. A com- 
pound must be homogeneous in structure. 

Compounds are very numerous—over half a million are known. 
Some common ones are: water, salt, washing soda, sand, alum, sugar, 
ammonia, copper sulphate, starch, China clay, glycerine, copper oxide, 
zinc chloride, magnesium chloride, chalk. 

Mixtures are the most commonly occurring of allthings. In these 
there is no definite structure in their smallest particles. Examples 
—milk, coal, tar, putty, flour, wood, glass, gunpowder, granite, fibres, 
air, soap, and most oils and fats. 

There is no invariable rule by which we can distinguish a pure 
substance (i.e. an element or compound) from a mixture. Sometimes 
the distinction is difficult to make, but as a rule it is fairly easy. The 
following are some of the principal differences between mixtures and 
pure substances in the solid form :— 


MIXTURES 
1. Constituents can be distin- 
guished by the eye, with or 
without the aid of a microscope. 


2. By solution and crystalliza- 
tion crystals of different kinds 
may be obtained. 


3. In many cases a particular 
solvent dissolves part of the mix- 
ture, leaving an insoluble residue. 


4. They have no definite boil- 
ing or melting points. 


II. SIMPLE TESTS 


PuRE SUBSTANCES 


1. The appearance is uniform 
throughout, however minutely 
they are examined. 


2. Solution and crystallization 
give crystals of one kind only. 


3. Substance dissolves thor- 


oughly and uniformly. 


4. Exhibit invariable and defi- 
nite melting and boiling points. 


FOR IDENTIFICATION OF COMMON 


SUBSTANCES used in trade or laboratory 


(a) Black Substances 
Manganese dioxide. 


Amorphous powder ; 


heated with hydro- 


chloric acid, yields a green gas of irritating odour called chlorine. 


Copper oxide. Amorphous ; 


heated in contact with hydrogen or 


coal gas, is reduced to metallic copper ; gently warmed with dilute sul- 
phuric acid, is dissolved to form a blue solution of copper sulphate. 


Charcoal. 


Insoluble in acids ; 


burns in oxygen or air to form 


carbon dioxide, which turns lime water milky. 


(6) Metallic Substances 
Copper. Soft red metal ; 


‘soluble in nitric acid to a green solution. 


36 TEXTILE CHEMISTRY 


Zinc. Hard and white; soluble in hydrochloric acid with evolu- 
tion of hydrogen gas. 


Lead. Soft; cut by a knife; rapidly tarnishes; insoluble in 
dilute hydrochloric and sulphuric acids. 

Magnesium. Burns with bright white flame ; very soluble in dilute 
acids. 

Aluminium. Very light; silver white; soluble in caustic soda 
solution with evolution of hydrogen. 

Iron. Grey; soluble in dilute sulphuric acid to a green solution 
with evolution of hydrogen; addition of nitric acid to this solution 
produces a darker and sometimes a black colour. 


(c) Coloured Substances 

Ferrous sulphate. Green crystals soluble in water ; if ammonia is 
added to this solution a blue precipitate is produced. 

Copper sulphate. Blue crystals soluble in water ; if a bright knife 
is immersed in this it becomes plated with copper. 

Mercuric oxide. Orange yellow or red: powder; when heated it 
darkens in colour, gives off oxygen, and forms a mirror of mercury 
higher up the tube. 

Red lead. Bright red powder ; heated, it evolves oxygen and turns 
to a straw colour ; gently warmed with dilute nitric acid, some dark 
brown lead peroxide is produced. 

Lead peroxide. Dark brown; gently warmed with hydrochloric 
acid, it evolves chlorine. 

Sulphur. Yellow crystals; soluble in carbon disulphide ; burns 
with a blue flame. 


(2) White Substances 

Potassium chlorate. When heated decrepitates, melts, effervesces, 
gives off oxygen, and leaves a white residue. 

Potassium nitrate. For shape of crystals, see Fig. 73, page 24 ; 
heated with strong sulphuric acid, brown fumes of nitric acid are 
evolved. 

Ammonium chloride. Heated with caustic soda, ammonia is 
evolved ; for shape of crystals on recrystallization, see Fig. 74, page 24. 

Marble. Dissolves in acid, liberating carbon dioxide, which turns 
lime water milky. 

Alum. Soluble in water, giving an astringent taste ; veld a white 
gelatinous precipitate on adding ammonia. 

Salt. Cubical crystals soluble in water ; insoluble in strong hydro- 
chloric acid. | 

Sugar (cane). Cubical crystals; sweet taste; soluble in water ; 
melts to a dark brown liquid ; strong sulphuric acid carbonizes it. 

Glucose (commercial). Yellow to brown solid ; not so sweet as cane 


PHYSICAL AND CHEMICAL CHANGES 37 


sugar; boiled with Fehling Solution, a bright red precipitate of 
cuprous oxide is formed. 

Sodium carbonate. Caustic taste; soapy feel; turns red litmus 
blue ; if as washing soda, it effloresces in air. 

Starch. Boiled with water, cooled, neutralized with acetic acid (if 
alkaline) and then tincture of iodine added, a blue colour is obtained. 

Dextrine. Soluble in cold water ; tincture of iodine added to this 
solution, a violet colour is obtained with the commercial variety. 

Bleaching powder. ‘Treated with dilute acid, chlorine is evolved ; 
very deliquescent as usually met with. 

Caustic soda. Very hygroscopic in air; forms strongly alkaline 
solution ; gives intense yellow colour to bunsen flame. 

Flour. Gives the reaction for starch, and is also turned yellow by 
strong nitric acid. 


III. PHYSICAL AND CHEMICAL CHANGES 


There is no such thing as constancy in nature—evolution and change 
are always taking place, in fact chemistry has sometimes been called 
the science of change. 

Rubbing a needle with a magnet will produce a change, as will 
rubbing a match on a piece of sand-paper. 

Mixing sugar and water causes the disappearance to sight of the 
sugar ; mixing sugar and water with strong sulphuric acid changes the 
first-named to carbon. 

Warming sulphur, or iodine, or alcohol changes the state of these 
bodies, and exposure of iron to the atmosphere changes it to rust. 

Careful examination of these and other examples shows us that all 
changes can be classified under one or other of two heads :-— 

(a) Physical change, in which the intimate constitution of the 
substance is not affected—such as ice into water, water into steam, 
boiling of alcohol, ether, etc., solution of sugar in water. 

(6) Chemical change, in which there is an alteration in composi- 
tion, the original substance being transformed into something else, e.g. 
action of sulphuric acid on sugar, action of heat on potassium chlorate, 
mercuric oxide, etc. 

Be careful not to define a chemical change as one brought about by 
the action of heat. All the various agencies are capable of bringing 
about both kinds of change. 

The following experiments result in the production of typical 
chemical changes :— 

1. Heat potassium chlorate in a tee tube, gas given off which 
reignites a glowing splint; white substance left. 

2. Heat mercuric oxide in a test tube, turns brown in colour; gas 


38 © TEXTILE CHEMISTRY 


given off which reignites a glowing splint ; globules of mercury sublime 
higher up the tube. 

3. Heat mercury and iodine in a test tube, violet fumes; then 
yellow, and ultimately a red sublimate formed. 

4, Rub iodine and mercury ina mortar ; first a green, ches yellow, 
then red substance formed. 

5. Expose bright sodium to air, tarnished on the nites 

6. Mix hydrochloric acid and ammonia gases, a solid in the form 
of white fumes is produced. 

7. Submit silver chloride to the action of light, it changes in colour. 


IV. HOW TO TELL IF A CHEMICAL CHANGE HAS TAKEN 
PLACE 


Look for :— 

. Change in texture, examining with a lens if necessary. 
. Evolution or not of gases. 

. Changes in solubility, boiling-point, melting-point. 

. Alteration in mass or volume. 

. Conduct with various reagents. 

. Evolution of heat or otherwise. 


. Action with well-known solvents, e.g. water, alcohol, carbon 
disulphide. 


IO or 0 Ne 


V. EXAMPLES OF PHYSICAL AND CHEMICAL CHANGES 
produced by various agencies 


HEAT 
1. Ice changed to water, water to steam. 
2. Volatilization of mercury, iodine, sulphur, etc. 
(Physical changes.) 
3. Decomposition of potassium chlorate, mercuric oxide, am- 
monium chloride, etc. 
4. Combination of iron and sulphur, copper and sulphur, lead and 
oxygen. 
(Chemical changes.) 


ELECTRICITY ; 
1. Current heating a wire or filament through which it travels, e.g. 
electric light. 
(Physical change.) 

2. The “sparking ”’ of gases. 

Hydrogen and oxygen combine to form water. 

Carbon monoxide and oxygen combine to form carbon dioxide. 

Ammonia gas is resolved into hydrogen and nitrogen. 


: 


PHYSICAL AND CHEMICAL CHANGES 39 


3. Decomposition of liquids and solids by a current in the process 
of electrolysis. 
Water into hydrogen and oxygen. 
Copper deposited from solutions of copper sulphate. 
Molten caustic soda or potash to produce the metal. 
(Chemical changes.) 


FRICTION 
1. Melting ice by rubbing pieces together. 
(Physical change.) 
2. Rubbing the head of a match on a rough surface. 
3. Rubbing iodine and mercury together in a mortar to produce 
mercuric iodide. 
(Chemical changes.) 


EXPOSURE TO THE ATMOSPHERE 
1. Action of freezing water on rocks and soils. 
2. Absorption of water by strong sulphuric acid, caustic soda. 
(Probably physical changes.) 
3. Phosphorus, iron, etc., oxidize in air, silver combines with 
sulphur. 
4, Phenomena of tarnishing, rusting, and fermentation generally. 
(Chemical changes.) 


SECTION V 
WATER 


ATER is one of the fundamentals of existence as we know 

N | it. It comprises three-quarters of the earth’s crust and 

is present in most natural things, in many of them to a 

very high degree, e.g. fish 80 per cent., animals (including man) up to 

70 per cent., plants 50 to 95 per cent., and even in clay up to 14 per 
cent. 

With one exception all the natural sources of water are more or less 
impure. The pure form is water vapour, which is always found in the 
atmosphere. From all surfaces of water 
exposed to the air evaporation is always 
taking place, and the water vapour so 
formed rises (because it is lighter than air, 
0-62: 1). It is thus cooled, and in the end 
condensed and falls as rain, etc. 

Rain- water in its fall dissolves gases from 
the atmosphere (oxygen, carbon dioxide, and 
nitrogen). This can be demonstrated by 
arranging the experiment shown in Fig. 83. 
When the water is heated, the gas is expelled 
and led by means of the funnel to the collec- 
ting tube. 

An average sample of rain-water will yield 
about 25 c.c. of gas per litre, of which tover 
30 per cent. will be oxygen, and nearly 3 per 
cent. carbon dioxide. 

Rain-water falling through a town’s at- 
mosphere will contain solid matter also. 
When the rain reaches the ground some soaks in (25 to 40 per cent.) 
and some runs along the surface, forming rivers and springs. This 
water contains solids as well as gases. They may be present in two 
forms :— 

1. Suspended solids. ‘These can be seen and may be removed by 
the process of filtration (Section III, page 27). Many of them are of 


40 


ee | ee ee eo ae 


Pe) oe eee 


WATER 41 


an organic character, e.g. canals and most rivers flowing through large 
towns are used for trade effluents which often contain a large amount 
of suspended matter. 

2. Dissolved solids. These can be removed by the process of dis- 
tillation only (Section III, page 21). The nature of the dissolved solid 
will depend upon the kind of strata over, or through which, the river 
or spring has passed, e.g. :— 

(a) Chalk or calcium carbonate in the Eastern and Southern 
Counties of England. 

(b) Sulphate of lime in the River Trent. 

(c) Magnesium salts at Epsom and in Durham. 

(d) Peaty matter on the Lancashire moors. 

(e) Chlorides of sodium and potassium in sewage effluents. 

The amount of solids found in water may vary from -032 gram per 
litre in Loch Katrine to 230 grams per litre in the Dead Sea. Dissolved 
solids alter the properties of water, particularly in reference to its 
action onsoap. Pure water, when mixed with soap, forms a lather and 
is said to be soft, but waters containing lime or magnesium salts pre- 
vent the soap forming a lather readily, and are said to be hard. (See 
practical exercises,. pages 43 and 44.) 

The hardness of and total solids in water are very important 
factors for consideration when deciding if a water is suitable for trade 
purposes. A water showing 5 degrees of hardness is termed soft, up 
to 18 to 20 degrees moderately hard, and over 30 degrees very hard. 

Very soft water is liable to dissolve metals such as lead, zinc, 
iron, etc., from pipes and storage vessels ; so for domestic purposes 
this water is sometimes “‘ hardened ”’ by the addition of lime. 

It is also usual to soften hard water by the use of lime or washing 
soda, or caustic soda or other chemicals. The rationale of the process 
where lime is used is as follows: The “ hardening salts ”’ are present 
as bicarbonates of calcium or magnesium, which are soluble in water. 
The addition of lime converts them into the normal carbonates, which 
are nearly insoluble in water, with the result that they are precipitated. 
If this precipitate be allowed to settle, the clear softer water can be 
withdrawn. This is known as Clarke’s process for water-softening. 

Sea water contains a large quantity of sodium chloride in addition 
to lime and magnesium salts. The presence of this substance is 
demonstrated by adding a solution of silver nitrate, when a heavy 
white precipitate is obtained. 

Pure water can be obtained from the natural sources by the 
process of distillation (Fig. 69, page 21). 

It should be (a) tasteless ; (b) colourless ; (c) odourless ; (d) com- 
pletely volatile ; (e) neutral to litmus and lacmoid ; (f) able to produce 
a lather when 50 c.c. of it are shaken up with 1 c.c. of standard soap 


42 TEXTILE CHEMISTRY 


solution. It has a b.p. of 100° C. or 212° F., and is a bad conductor of 
heat and electricity. ? 

As an exercise in the preparation of pure water, fit up the apparatus 
shown in Figs. 84, 85, 86. Reject the first portion which comes over, 


VAM 


Pa a 


) 

Le 

VN Fig 85 
Fig 84 


as this might have dissolved some matter in passing through the glass 
tubes. When obtained, perform the following experiments :— 

_ (a) Evaporate some to dryness ; 
evaporate the same quantity of 
well water or spring water, canal 
water or tap water, and compare 
the residues by inspection and by 
weighing. 

(b) Taste it, and compare the 
taste with tap water. 

(c) Note its action on litmus 
and lacmoid. 

(dq) Find how many drops of 
standard soap solution are required 
to produce a permanent lather 
with 10 c.c. of it. Compare with 
the amount required by 10 c.c. 
of tap water. Shake well after 
adding each drop, use a test tube and close tightly with the thumb. 

(ec) Add a few drops of silver nitrate solution. What occurs ? 
Compare with tap and canal water. 


aa 


hi 


Pe ee ee i i ee ee 


WATER 43 


A simple analysis of a natural water to determine suitability for 
textile purposes should include the following :— 


1. Determination of total solids. 

Weigh a clean dry beaker, put in 200 c.c. of the water to be tested, 
and keep in a steam oven until evaporated to complete dryness. 
Weigh again. Increase = Total solids in 200 c.c. Calculate to 
100,000, ic. x by 500. After weighing, dissolve the residue in a few 
drops of dilute hydrochloric acid. 

Note if carbonates are present—effervescence. 

Test for sulphates by adding to a few drops of the liquid some 
barium nitrate solution. White precipitate if present. 

Test for lime. To another portion of the solution, add ammonia, 
ammonium chloride, and ammonium oxalate solution. White preci- 
pitate = Lime. 


2. Determination of total hardness. 

Take 50 c.c. of water in a bottle provided with a tight-fitting cork. 
Put “ standard soap ” solution in a burette (Fig. 21, page 5), and run 
it into the water a few drops at a time, shaking well after each addition. 
Repeat until a permanent lather is produced which lasts without 
breaking for three minutes when the bottle is laid on its side, and is about 
4 inch thick. Perform the experiment three times, find the average 
amount of soap solution used, and by consulting the Table of Hardness 
(page 44) find the degree of hardness of the water. 


3. To determine permanent hardness. 

(Permanent hardness is due to the presence of hardening salts, 
which are not removed by boiling the water.) Take 250 c.c. of the 
water and boil gently for half an hour. Filter quickly, and when cold 
make up to the original volume with distilled water and mix thor- 
oughly. Find the amount of soap required by 50 c.c. as for total 
hardness, and obtain result in a similar manner. 


4. Temporary hardness. 
Obtained by calculation. 
Total — Permanent = Temporary. 


5. To test for metals. 

Put some water in a white porcelain dish, stir with a glass rod 
which has been dipped in ammonium sulphide. Blackening = iron, 
lead, or copper. Add a few drops of acetic acid. Colour disappears 
= iron; colour remains = lead, or copper, or both. 


Af TEXTILE CHEMISTRY 


TABLE OF HARDNESS 


(Hardness of water expressed as grams of calcium carbonate per 
100,000 c.c. of water.) 


c.c. Soap. Gm. CaCO. c.c. Soap. Gm. CaCO3. c.c. Soap. Gm. CaCQ3. 


7-43 11-0 14-84 
8-14 11-5 15-63 
8-86 12-0 16-43 
9-57 12-5 17-22 
10-3 13-0 18-02 
11-05 13°5 18-81 
11:8 14-0 19-6 
12-56 14-5 20-4 
13:3 15-0 21-19 
14-06 15:5 22-02 


c ho 
ota OO 


Or 


onl 


1-0 
1-5 
2:0 
2°5 
3:0 
3:5 
4-0 
4-5 
5-0 
5.5 


DH OE Co 8 tO 
WOW AON 

— 

— 
SPOEVOVNHAADS 
ROMOROAens 


For volumes of soap solution used .between those given in the table 
estimate the grams of calcium carbonate, e.g. 3:2 c.c. = 3-51. 

If more than 15-5 c.c. of soap solution are required, 25 c.c. of the 
water being tested should be used, 25 c.c. of distilled water added, and 
the hardness so obtained multiplied by two. 

Standard soap solution is prepared by dissolving pure soap in a 
mixture of ethyl alcohol (2 vols.) and distilled water (1 vol.), 
allowing the mixture to stand a few days, decanting the clear liquid 
and setting this against a “standard hard water” until it is of such 
a strength that 14:2 c.c. of soap solution are required to form a 
permanent lather with 50 c.c. of standard hard water. 

Standard hard water is made by dissolving 0-4 grams of pure 
marble in hydrochloric acid, driving off the excess of acid, and dissolv- 
ing in 2 litres of pure water. This water has a hardness equal to 20 
grams of calcium carbonate per 100,000 c.c. of water. 

The principle of the construction of a continuous water-softening 
plant can be illustrated by arranging the apparatus as shown in Fig. 
87. Hard water is placed in the aspirator and allowed to flow to the 
bottom of a large test tube which is divided into two compartments by 
a perforated cork. In the bottom is put milk of lime, and in the top 
is packed cotton wool. The exit pipe is covered with filter paper. 
The hard water is softened when in contact with lime, passes through 
the cork, and the precipitated chalk and excess of lime is filtered out in 
its passage upwards, with the result that a much softer water is col- 
lected in the beaker. The bottom of the test tube may be surrounded 
with a vessel containing warm water, when the efficiency is increased. 

With a piece of apparatus arranged as shown, water requiring 16 
c.c. of standard soap solution per 20 c.c. was softened to one requiring 
only 4 c.c. 


WATER 45 


When a fairly strong current of electricity is passed through acidu- 
lated water, it is decomposed into hydrogen (2 vols.) and oxygen (1 vol.) 
(Fig. 88). Hydrogen is liberated where the current leaves, and oxygen 
where the current enters the liquid. If the gases be collected together 


(Fig. 89), and the mixture sparked, they recombine with explosive 
violence to form water. 

The synthesis, or building together, of water, may be studied by 
using the apparatus illustrated in Fig. 90. 


46 TEXTILE CHEMISTRY 


Hydrogen is generated from zinc (B) and dilute sulphuric acid (A) 
dried by bubbling through strong sulphuric acid (D) and then passed 
over heated copper oxide contained in a hard glass tube (C). The 
copper oxide is reduced, the oxygen combining with the hydrogen 
to form water, which is collected in the U tube E, containing an 
absorption agent such as calcium chloride. 


Results obtained in an actual experiment with this apparatus :— 


Wt. of tube + Copper oxide before heating = 42-179 gm. 
” Teas 9 29 after re = 42-150 ,, 


I 

S 
bo 
© 


.. Oxygen used 


Wt. of calc. chlor. and tube after absorption = 41-653 gm. 
before - = 41-620 |, 


9? 29 99 


! 
> 
& 


.. Water produced 


Hydrogen used = -033 — -029 = -004 gm. 

Ratio = 1: 7-25. 
Chief uses for water— 
1. Domestic purposes—washing, cleansing, food, drink. 
2. To generate steam for motive and other purposes. 
3. For motive purposes—water mills, turbines, etc. 
4. Irrigation, navigation, solution, etc. 
5. Water vapour forms an “earth blanket.” 


SECTION VI 


I. GASES 


GAS has neither definite shape nor size; it possesses the 
property of expansibility. Some gases are light, some heavy, 
some coloured, some invisible, some elements, some com-_ 
pounds, some mixtures, some soluble in water, some nearly insoluble, 
but certain properties they have in common. 


Relative Soly. in 


Name of Gas. Density. Talay, Smell, Colour, etc. 


Element ; No smell 
Mixture Smell due to im- 

purities 
Compound No smell 
Pungent 


Nitrogen . 
Carbon monoxide 


No smell 


Air ‘ 
Nitric oxide : 
Oxygen . ; 
Hydrogen sulphide , 
Hydrochloric acid 
Carbon dioxide . 
Nitrous oxide . 
Sulphur dioxide . 
Chlorine , 
Bromine . 


Brown fumes in air 
No smell 

Fotid smell 
White fumes in air 
Faint acid smell 
Laughing gas 
Suffocating 

Green colour 
Brown colour 


HE OO OOOROROBA 


To find the weight of a given volume of gas, exhaust a globe and 
counterpoise it (Fig. 91). Fill with gas and reweigh. Jind its 
volume by measurement of diameter and calculation. Volume of 
ie y Bata ae aot 

3 7 

To find the solubility of a gas, fit up the apparatus as shown in 
Fig. 92 (or Figs. 66, 67, pages 18,19). The graduated tube is filled 
with the gas over mercury and the solvent is put in the cup. 

When the tap is cautiously opened, a few drops will fall into the 
tube and float on the mercury. The tap is closed, and the liquid 


47 


48 TEXTILE CHEMISTRY 


allowed to exert its solvent action on the gas. As it does so the 
mercury rises in the tube. 
Some general methods for prepara- 
tion of gases— 
1. Boil liquids. Water, ether, alcohol, 
carbon disulphide. 
2. Heat solids. Wood, coal, iodine, 
chlorate of potash. 
3. Treat solids with acids. 
Copper and nitric acid—brownish 
red gas. 
Copper and sulphuric acid—sul- 
phur dioxide. 
Zinc and hydrochloric acid — 
hydrogen. 
Marble and hydrochloric acid— 
carbon dioxide. 
Salt and sulphuric acid—hydro- 
chloric acid. 
Manganese dioxide and hydro- 
chloric acid—chlorine. 


Fig 9 


Pr ee eee a a 


GASES 49 


4. Treating a liquid with a solid. Water and sodium or potassium 
give hydrogen (Fig. 98). 
5. From a mixture of two gases remove one. Burn phosphorus in air 
—nitrogen is left (Fig. 107, page 54). 
6. Electrolysis of liquids. Water to hydrogen and oxygen (Fig. 88, 
page 45). 
Some general methods for collecting and storing gases. 
1. In gas jars or tubes over a liquid, usually water, in a pneumatic 
trough (Fig. 94). 
2. By displacement of air (Fig. 95). 
For gases heavier than air, see Fig. 95 (a). 
29 ” lighter 29 oe) 9 95 (0). 
3. Passing into an aspirator (Fig. 96). By this arrangement the 
volume collected or used can be measured exactly. 


A) Fie 95 bb) Fig 96 


GENERAL PROPERTIES OF GASES 

All gases expand when heated and contract when cooled, and the 
rates at which they do so are the same in all cases—approximately 
1/273 of the volume at O0°C. for each degree Centigrade. 

This general property is summarized and expressed mathematically 
in the form called Charles’ Law. 

A simple piece of apparatus for its experimental verification is 
shown in Fig. 97. The flask A is full of gas (say air). It is kept 
immersed in the beaker B by a lump of lead C. The mouth of the 
flask is closed by a cork, through which passes a delivery tube D. 
When the water is heated the gas expands, the excess being driven out 
through the tube. The temperature is taken before heating the gas, 
and the heating continued until the water boils. 

The expansion is measured by allowing the flask to cool with the 
end of the tube under water, when the water rushes back to fill the 
place of the expelled gas. The volume of A is measured, and then the 


4 


50 TEXTILE CHEMISTRY 


increase calculated for 1 c.c. for 1 degree Centigrade rise in temperature. 

Accurate determinations of the coefficient of increase of volume of 
a gas at constant pressure can be made by using the form of apparatus 
illustrated in Fig. 98, which was designed by the author and used 
in his physics laboratory at the Mundella School, Nottingham, some 
twenty-five years ago. 


cgi ipa, ei op Selle a atiens Rane 


Pe SR 5 ee ee a te ye et 


ee eT em a 


The “ Constant-pressure Air Thermometer’ 
shown in this diagram was first published a 
the author (and awarded first prize) in con- 
nexion with a competition organized by Messrs. 
Newnes in their publication Technics in 1904. It 
is republished with their permission. 


Method of Using. The gas is enclosed in one limb of a U 
tube by means of mercury, which can be kept at constant level by 
withdrawing from the tube joined to the bottom of it, or by filling in at 
the top of the longer limb. 

The portion of the tube containing the gas is graduated so that 
volumes may be read, and these graduations are continued on the other 
limb to enable a constant level to be obtained accurately. 


GASES 51 


The bath is filled with cold water, the pressure adjusted, and the 
volume and temperature read. Steam is then passed in and the tem 
perature gradually raised. At intervals of (say) 10°C. the pressure 
is again equalized and the volumes determined. The expansion per 
unit volume for unit rise in temperature may then be calculated. 

Boyle’s Law. The volume occupied by a gas is also dependent 
upon the pressure on the gas ; this is illustrated in a pop-gun or air-gun. 
Boyle investigated the problem of “the spring of air” long ago and 
found that for a given mass of gas at a constant temperature the 
volume was inversely proportional to the pressure, i.e. 


a 
Pressure of Gas 


Fia.101 Fig.102 
If the pressure was doubled the volume was halved. 
oe) ”? ”? trebled 9 5 made one-third. 
2 i », quadrupled __,, +>,  One-fourth, etc. 


His apparatus is illustrated in Fig. 99. Pressure gauges may be 
constructed on this principle. Ifthe tube is open at the end, it is called 
a manometer (Fig. 100), and it can be used to measure the pressure of 
a gas, say the domestic gas supply, in inches of water. 

Diffusion. The particles of which gases are composed are always 
in motion. They are thus able to :— 

1. Mix with each other irrespective of relative densities, e.g. if a 
jar of hydrogen be inverted over a jar of oxygen, at the end of a few 
minutes each jar will be found to contain an explosive mixture of 
oxygen and hydrogen (Fig. 101). 


52 TEXTILE CHEMISTRY 


2. Pass through a solid partition which contains pores, such as 
unglazed porcelain (Fig. 102). This phenomenon is known as dif- 
fusion. 

Graham, who investigated the problem, found that the rate of 
diffusion was inversely proportional to the square root of the densities 
of the gases, e.g. density of hydrogen = 1, density of oxygen = 16. 
Square roots of these numbers = 1 and 4. Then rates of diffusion 
are 1:4. 

IDENTIFICATION OF GASES 

Many gases, if they are pure, can be recognized easily by certain 
simple tests, thus :— 

(a) Action on a glowing splint. 


CO). ates 5, 2 lighted taper. 

(c) “1 ,, wet litmus paper—red and blue. 
CMe ,, lead acetate paper. 

(e) 4, 4, potassium chromate paper. 

(f) A ,, Starch paper. 

Gye ve, ,, Starch iodide paper. 

(ie) nee. ,, a drop of ammonia on a glass rod. 


Gases recognized— 
1. From their appearance—chlorine (green), hydrochloric acid 
(white fumes), nitrogen peroxide and bromine (brown), iodine (violet). 
2. By their odour—chlorine (irritating), ammonia (pungent), sul- 
phuretted hydrogen (fcetid), sulphur dioxide (suffocating). 
3. By glowing splint test—oxygen and nitrous oxide (re-ignite). 
4. By combustibility—hydrogen, sulphuretted hydrogen, carbon 
monoxide. 


PRACTICAL EXERCISES 


Try to identify the gas evolved in each of the following experi- | 


ments :— 

. Heat a mixture of potassium chlorate and manganese dioxide. 
. Warm some ammonium chloride with caustic soda. 

. Act on sodium sulphite with dilute hydrochloric acid. 

. Heat lead peroxide with strong hydrochloric acid. 

. Warm some aluminium with caustic soda solution. 

. Heat oxalic acid crystals with strong sulphuric acid. 


II. THE ATMOSPHERE. 


Oo rF WH 


Air is the most important of man’s necessities. We can live several — 
days without food, several hours without water, but not more than ~ 


two or three minutes without air. Its physical and chemical proper- 
ties have been subjects of investigations for generations, and the 
following conclusions have been established :— 


ne See Raed 


, bes 


= aia ly 


a ee ee 


eg ee Sp RT ee ae, Sen ee ee 


AIR 53 


(a) It is necessary to life and combustion. All other gases are 
useless, poisonous, or asphyxiating so far as animals are concerned. 
To get a fire up, we must allow air to have access to the coal. To put 
it out, we cover it up to prevent air getting to it. 

(6) Fresh air is also necessary, or 

(c) Its power of supporting combustion is limited. To illustrate 
this, burn a candle under a bell jar (Fig. 103). Other facts illustrating 
the same truth are the Black Hole of Calcutta episode, the necessity for 
ventilation of inhabited buildings, open-air treatment of consumption. 


F1G.105 


FIG. LO4 


(d) Boyle noticed that when metals were exposed to, or heated in 
contact with, air, they were altered in appearance and gained in weight, 
forming what he called a calx. Examine the calces of lead, copper, 
iron, zinc, mercury. 

(ec) In these processes a portion of the air is used up. This can be 
demonstrated by putting a muslin bag of iron filings in a jar of air and 
inverting over water for several days (Fig. 104), or using phosphorus 
in a longer tube (Fig. 105). Lavoisier’s original apparatus is shown in 
Fig. 106. He treated mercury for several days in his retort, and found 
that the air gradually decreased in volume until there was no further 
contraction, and that specks of red appeared on his mercury. When 
these specks were strongly heated, they yielded a gas which gave the 
same volume as that lost by the air, but this gas was much more active 


54 TEXTILE CHEMISTRY 


than original air, and was identical with a gas, named oxygen by him, 
obtained by other methods. 

(f) The portion left does not act like original air, and was called 
dephlogisticated air, or azote, now named nitrogen. Therefore 

(g) The atmosphere is considered to consist of two gases at least. 

To determine the proportion in which these two gases exist. (The 
original method of Lavoisier is unsuitable for general use.) The sim- 
plest way is to burn some phosphorus in a bell jar of air standing in 
some water. The phosphorus can be ignited by warming the end of 


Fig. 107 


a metal rod and quickly inserting the stopper which carries it. The 
volumes of original and residual air should be marked with strips of 
gummed paper (Fig. 107). | 

Accurate method. Use the apparatus shown in Fig. 108, which 
consists of a bottle containing a known volume of air, fitted with a 
rubber stopper through which pass the delivery end of a stoppered 
burette and a manometer tube. 

Put into the burette a little strong solution of ‘‘ Pyro ” in water, 
and fill up with caustic soda solution. Read level of liquid in the 
burette. Allow a little pyro-soda to pass into the bottle and shake 
carefully. Some of the oxygen is absorbed, and, the pressure of air in 


AIR 55 


the bottle being thereby decreased, one arm of the mercury falls, and 
the other rises in the manometer. Allow more solution to flow into 
the bottle until the surfaces of the mercury columns become perma- 
nently level. Read the burette, and so find the volume of liquid 
passed into the bottle—this is equal to the volume of oxygen in the 
original volume of air. Calculate the percentage. The volume of 
nitrogen is found by difference. In round numbers the result should 
be 21 per cent. of oxygen, 79 per cent. nitrogen by volume. 

Other constituents. Careful and exact experiments have shown 
that, besides oxygen and nitrogen, there are present in air (a) water 
vapour; (b) carbon dioxide; (c) argon; (d) traces of nitric acid, 
ammonia, ozone, etc.; (e) solid matter; (f) living organisms known 
as bacteria or germs. 

The presence of water vapour is proved by rain, clouds, etc., and by 
the exposure of hygroscopic substances to air, e.g. strong sulphuric 
acid increases in weight and gets weaker. 

Solid caustic soda or potash becomes wet. 

Dried cobalt chloride (on filter paper) becomes pink in a damp 
atmosphere. 

At 0° C. 1 cu. metre of air can hold about 5 grams of water vapour. 


ood Ua ag Ae - ae eh i Shi Paes ~ ni 
mapo US) ,, ts Bey si, peels (14) 4 a 
mee Cabs; ie wer 2 rm Wiisoere wa he 
” 30°C. 1 ” ” 29 9 9 30-0 ce) 9 ” 


Therefore its point of saturation depends upon the temperature. 
Air near its point of saturation is said to be humid, and it has a very 
enervating effect on the human system, particularly at the higher 
temperatures. 

A certain degree of humidity is necessary in a weaving shed. For 
certain classes of goods the ordinary atmospheric condition of Lanca- 
shire is sufficient to ensure it, but for others it is necessary to supply an 
artificial humidity. ‘To guard against this being carried to excess, the 
manufacturer who steams is compelled to determine and record three 
times per day data from which the percentage humidity of his shed 
can be calculated. 

To determine relative humidity. The only accurate way for finding 
humidity, is to pass a known volume of air through a desiccating agent 
which can be weighed before and after the experiment. This necessi- 
tates accurate apparatus, and requires considerable time, during which 
the proportion of moisture present can have changed considerably. 
Therefore it is not usual to use this method, but one due to Mason 
known as the wet and dry bulb hygrometer, in conjunction with 
Glaisher’s Tables, which have been compiled from results obtained by 
an accurate method. 


56 TEXTILE CHEMISTRY 


Two thermometers are needed, the bulb of one being covered with 
muslin, which is kept wet by immersion in a small vessel of water. If 
the air be not saturated with moisture, evaporation takes place from 

‘this muslin, with the result that the temperature of this thermometer 
is lowered. The drier the atmosphere, the more the evaporation and 
consequently the lower the reading will be (Fig. 


D et 109). | 
To find percentage humidity. 
Take the reading of each thermometer simul- 


OR taneously. 
WR Say dry bulb reading is 22°C. 
uslin 4. Wet 29 ” 9 18°C. 


Find the difference 22 —18 = 4° C. 
Water Use the table as follows :— 


Fic. L109 Go to the line for the dry bulb reading, i.e. 22, 7 


and in this line find two factors :— 
(a) That given in the 0 column = 19-7. 
CO) Sitse - , difference 4 column = 12-9. 
12:9 x 100 


Then percentage humidity = a x 100 or 19-7 


HUMIDITY TABLE 


Reading of Factors ” when Difference between wet and dry Bulb is 


Dry Bulb 
in deg. C. 0 1 2 


—_———— | | LN 


DIDHAN 
Or OL 9 9 Db 
Ot 69 G9 ND BO Rt 


bo 

bo 
WDD NNNDDN HH BB Be Bee eee 
FAO WO BDAWN SD OIAAPE WWM MOOS 
OOK NOANONOPRRP PK ONO WD O1O LO 
RD bo DOD DDD BS ee ee eS Re eS 
eee een eee Se 
DMNOOORAWODMATNWWDOKWRAWONAOS 
DD DD DD DOD Ee 
Nase Noa Di ge PR atch am ictal ont fle cl onda whi ghar ea 
OWWAWOTNRPWNK KE NWOANON DOD 
BS 0D DD DD ee ee ee eS 
Fi 0S SOS ae EN eS BOS Te See 
OK AWWOMAHAANUITNIAWOKWHAOCWoONs* 
BSD ee 
BS Fo 00 30 We G9 BS BS Re e908 ote Se OU CES 
NOK WARPNOCHOCOKWANTORNTNAHS 
BD i ; 
DS DAT D OB 69 WD SO HD ATH DN Tri HO 
AEH oOOPWWWROATNOHE PDH DOTS 
ell moni sorlll cool woe aeeelll eel eal 
oad Tah ener tha Ri ide i ed : 
CON OWATWUDGSOWNWDNAOKP OKO 
te eel cael cell aoe asl ee 
lc wich oC ab air eliaidicts : ate 
AWO HHS HDPE RON TOW WWOWO MN 


= 65-5 per cent. 


a ie oe 


yp ie ee at 


Pai ae 


AIR 57 


Home Office Regulations provide that no artificial humidification 
will be allowed in any weaving shed where steaming is carried on when 
the wet bulb reading of the hygrometer exceeds 75 deg. Fah. (i.e. 
24°C.). Previously steam was allowed to be infused until the wet bulb 
thermometer registered as high as 91° F. or 33°C. The readings have 
to be entered three times a day jointly by representatives of the firm 
and the operatives. 

The presence of carbon dioxide is proved by aspirating a good 
volume of air through baryta water or lime water (Fig. 110), which is 
turned milky by the gas. It is derived from the combustion of carbon 
and carbon compounds, and respiration of animals. The assimilation 
of it by plants keeps the gas from accumulating in excess of -04 per cent. 
by volume. It may however be locally in excess, e.g. in crowded 
rooms, smoky towns, mines, etc. 

Carbon dioxide in air can be estimated approximately by the Angus 
Smith test, and accurately by the Pettenkofer method. The other 


constituents require more accurate and refined methods for their 
identification. 

Estimation of carbon dioxide in air by Angus Smith method: Take 
bottles of various capacities ranging from 100 c.c. to 580 c.c. and fill 
them with samples of the air to be tested. To each add 14 c.c. of a 
clear saturated solution of lime water and shake. Note the smallest 
bottle in which a milkiness is produced. Refer to the graph (Fig. 111) 
and find the percentage of carbon dioxide which is given for its capa- 
city, e.g. if 185 c.c. then percentage = -1; 300 c.c. = -06 per cent. ; 
445 c.c. = -04 per cent. 

At its best, Smith’s test is but a rough-and-ready method. 

The Pettenkofer Method in one or other of its numerous modi- 
fications is always used if we require a quantitative result. Its 
manipulation is delicate and requires much practice before accuracy 
is attained, particularly in normal air determinations. 

As an exercise for the beginner, good and interesting results can be 
obtained with it for expired air working ag follows :— 


TEXTILE CHEMISTRY 


58 


In the small flask put 


made by shaking baryta with 


5) 


-saturated baryta water 


Arrange apparatus as shown in Fig. 112. 


20 c.c. of semi 


+39 U1 at 0g, peters 
00% eh Ea pooe ; “29007 "22 QOL 


“UZYOUS PUD PIPpo 21D 
adPOM uly] P2FAINJDOS IDI]D JO IZ] VY 
‘APMsay 2143 so u2y02 $> prorrposd St SOUP YW 
1 YNYA In THY JO MNOg as2ppouss Mp, 30 Anroodwo 24 7 


Sy ae er es 


Tee | 


AIR 59 


distilled water, and when saturated decanting, and diluting with an 
equal volume of water. 

Blow air from the lungs slowly through this solution and measure 
the water expelled from the aspirator, which will be approximately 
equal to the volume of expired breath. A suitable amount to pass 
through is 1,000 c.c. When finished, disconnect the flask. 

In a similar flask put another 20 c.c. of the original baryta water, 
and to each add 2 or 3 drops of an indicator called phenolphthalein. 
A pink colour is produced. Now from a burette run in a standard 
solution of oxalic acid containing 5-65 grams of the pure acid dissolved 
in one litre of water. 

Find the volume required just to destroy the pink colour in each 
case. It will be found that less is required by the baryta through 
which expired air has passed. The difference can be utilized to 
measure the amount of carbon dioxide which has passed through. 


Suppose the difference = 37 c.c. 
Now | c.c. of oxalic acid of above strength = 1 ¢.c. carbon dioxide. 
Then 37 c.c. Pe 29 ” 9 = 37 ¢.c. 9 9 


which is present in (say) 1,000 c.c. of expired air, i.e. = 3-7 per cent. 

The amount of carbon dioxide in air can be taken as an index to 
the efficiency of the ventilation of a building. A high percentage of 
the gas means a vitiated and unhealthy atmosphere. 

A Parliamentary Committee Report issued in 1909 said, “ The 
greatest evil in a mill is the lack of efficient ventilation,” and this 
remark could well be extended to English buildings generally, including 
dwelling-houses, and particularly bedrooms. 

Principles of ventilation are well understood by scientific experts, 
but the application of them seems to make very little headway, due to 
general ignorance or carelessness and stupidity on the part of the 
British public. 

~ One of the purest atmospheres in a public building in the United 
Kingdom is that of the British House of Commons. This is due partly 
to the fact that (as a rule) the number of people in it is small, but 
chiefly because it is ventilated on a system. 

The “ draught ” is supplied by a shaft running up one of the famous 
towers, and the air drawn in is washed, warmed, filtered, and then 
allowed to enter under the benches. It rises towards the ceiling and 
is extracted at such a rate that no strong current is produced. 

Air which contains dust is distinctly dangerous to health. Pro- 
fessor Tyndall once made the famous remark, “‘ Shut your mouth, and 
save your life,” meaning thereby that you should breathe through the | 
nose, the hairs in which arrest many of the solid particles. 

Every solid particle is a small world on which may rest hundreds 


60 TEXTILE CHEMISTRY 


of spores, microbes, or germs capable of producing pulmonary and 
gastric troubles and, it may be, disease and death. 

A simple piece of apparatus which can be used to trap and estimate 
the bacteria in air is shown in Fig. 113. 

A is a small tube containing sterile water through which air may be 
drawn by attaching to B, which in its turn is connected to C by means 
of a flexible rubber tube. 


Tic 113 


By suction at the tube D the water can be started running from B 
to C, which thus causes a similar volume of air to bubble through A. 

By interchanging the flasks when C is empty, and repeating the 
process, more air is bubbled through the water in A, and if the volume 
of water used is known the exact volume of air passed through can be 
calculated. | 

An aliquot part of the water in A is plated on sterilized gelatine or 
agar and cultivated, when each bacteria will produce a “ colony ” if 
incubated at a suitable temperature. 


SECTION VII 


I. OXYGEN 


XYGEN is the most abundant element in the world—half the 
() crust of the earth, eight-ninths of water, and one-fifth of air 
is composed of it. 

It was originally obtained from calx of mercury, first as an 
“unidentified spirit ’’ by Eck de Sulzbach in 1489, and later by Priest- 
ley in 1774. Scheele had prepared the gas in 1773, but had not pub- 
lished the fact. The gas can be prepared in a great many ways, the 
most important of which are :— 

1. By heating oxides which evolve the gas, e.g. mercuric oxide, 


manganese dioxide, silver oxide, barium peroxide, red lead, lead 
peroxide, etc. 

2. By heating potassium chlorate, particularly if mixed with man- 
ganese dioxide (Fig. 114). This is the usual laboratory method of 
obtaining the gas. 


61 


62 TEXTILE CHEMISTRY 


3. By heating certain substances with sulphuric acid, such as 
potassium dichromate, potassium permanganate, manganese dioxide. 

4. From bleaching powder by warming it with water to which has 
been added a little cobalt nitrate (to produce cobalt oxide, which acts 
as the decomposing agent). 

5. By evaporation of liquid air. Nitrogen boils at a higher tem- 
perature than oxygen, so, if liquid air be distilled under certain condi- 
tions, oxygen is first evolved. ‘This is how oxygen is now prepared 
commercially: 

6. By the interaction of solutions of potassium permanganate and 
hydrogen peroxide in the presence of sulphuric acid (Fig. 115). Inside 
the small bottle is a smaller one. Hydrogen peroxide is put in one, 
acidified potassium permanganate in the other, and the bottle is then 
connected with the Hempel burette. On tilting the apparatus, the 
liquids mix, oxygen is evolved and collects in the limb of the burette. 


a | 


Fig.116 Fig. 117 


Oxygen is a very active gas; glowing splints, carbon, phosphorus, 
sulphur, and even iron wire burn in it with great energy, in most cases 
to form oxides. The operation is conducted with a deflagrating spoon 
as shown in Fig. 116. 

T'o determine the volume of oxygen evolved by heating a substance 
which yields it, use the apparatus shown in Fig. 117. Weigh the empty 
tube, put the substance in and reweigh. Attach it to the aspirator as 
shown and collect the water expelled from the delivery tube. Measure 
it and calculate the volume obtained from 1 gram of the substance. 

As an exercise, use potassium chlorate. 

T'o find the weight of oxygen expelled when a substance is heated, or 
to find the weight which combines with a substance when heated in 
air, use a crucible, etc. (Fig. 44, page 12). 


ee ee me 


a ae ee 


OXYGEN 63 


EXERCISES 


1. Find the weight of oxygen expelled from 100 grams of potassium 
chlorate when strongly heated. 

2. Take a piece of magnesium ribbon about 2 feet long, clean it 
with sand-paper, weigh it and divide into two equal parts. Burn one 
piece in air by heating on a crucible lid over a bunsen flame. Carefully 
collect all the calx and weigh. 

Compare with the weight of magnesium used. 

Dissolve the other piece in two or three drops of dilute nitric acid 
on a crucible lid. Heat to dryness and until all brown fumes are 
driven off. Again collect the white powder, weigh and compare with 
the weight of calx from the previous experiment. ‘Taste to see if it 
is magnesia (Magnesium oxide). 


II. OXIDATION AND OXIDES 


The act of chemical union with oxygen is known as oxidation. If 
the substance which is oxidized is an element, the compound produced 
is called an oxide. An older name is calx. 

Nearly every element combines with oxygen under one condition 
or another, directly or indirectly, to form an oxide, and some produce 
2, 3,4, oreven 5. More than 100 different oxides have been prepared. 

Iron oxidizes in moist air to form iron oxide ; it is termed rusting. 

Lead and copper both tarnish in air, especially if heated, due to 
oxidation. | 

N.B.—Tarnishing does not always denote oxidation, e.g. the 
tarnish on silver is due to the formation of a sulphide, not an oxide. 

Phosphorus, sodium, potassium need only to be exposed to air for a 
few seconds to bring about oxidation. 

Aluminium, zinc, magnesium, tin, mercury do not easily oxidize to 
a notable degree in ordinary air at ordinary temperatures. 

Other oxides may be produced by calcination or roasting, i.e. heating 
in air or oxygen. Mercuric oxide, magnesium oxide, tin oxide, zinc 
oxide, the oxides of carbon and sulphur may all be prepared in this 
way. 

Another method which may be employed is to use substances which 
will readily yield oxygen, such as nitric acid, bleaching powder, potas- 
sium chlorate, hydrogen peroxide, etc., and which are therefore called 
oxidizing agents, e.g. :— 

1. Add strong nitric acid to tin, white tin oxide is formed. 

2. Take some cobalt nitrate solution in a test tube. Add two or 
three drops of sodium hypochlorite (note the formation of black oxide 
of cobalt). Add it to an emulsion of bleaching powder and water and 
gently warm. ‘Test the gas evolved. What is it ? 

3. Heat, with constant stirring, a small piece of lead in a crucible 


64 TEXTILE CHEMISTRY 


lid. Note the changes that occur. ‘Try to get some litharge. Did 
you? If so, state what it was like. 

4. Oxidize some red lead by warming it with dilute nitric acid. 
Describe the product. How many oxides of lead have you seen? — 
Compare and contrast them. 

5. Take a few drops of mercuric chloride. (Be careful: this is a — 
deadly poison.) Add caustic soda solution. What happens ? Filter off 
the precipitate. Carefully dry it and then heat it strongly in a small 
ignition tube. Can you identify the gas evolved ? Ifso, state what it is. 


III. COMBUSTION 


is often an act of oxidation. Lavoisier was the first chemist to explain it — 
assuch. The old theory was that when a substance burned it lost some- — 
thing, known as phlogiston, and it was then — 
unable to burn again until it had been treated — 
with a substance rich jin phlogiston, such as — 
carbon, which supplied it with some. | 

Lavoisier’s theory of combustion was, that — 
when a substance burned it gained something, — 
that something being oxygen, obtained either — 
from the air or a substance capable of yielding — 
it. , 

This explains why substances burn in ordi- 
nary air or oxygen, and why they refuse to burn 
in the inactive four-fifths of air which contains 
no oxygen. 

fic. 118 Apparently when a candle burns it loses 

weight, but if an apparatus be arranged for it to 
burn in, so that all the products of combustion are trapped and also 
weighed, it is found that there is a gain and not a loss (Fig. 118). 

Sulphur and carbon burn in gunpowder at the expense of oxygen in 
nitre, which is one of the constituents of gunpowder. 

As a rule, chemical combination with oxygen results in the produc- — 
tion of a large amount of heat, sometimes sufficient to make the body : 
red, or even white hot, and sometimes flame is produced. | 

This is very liable to occur in heaps of oily cotton waste. The oil 
is oxidized by the oxygen of the air and gradually the temperature is — 
raised until it is sufficient to produce and ignite a vapour from the oil ; 
and so we get the starting of a fire, which still is far too common in ' 
Lancashire mills. 


Pg Re te eae ea La ene te oe a ae eee eee 


he Sinema ie 


IV. BREATHING 


is also an act closely connected with oxidation, being a process for 
supplying oxygen to the blood and removing carbon dioxide from it. 


OXYGEN 65 


The warmth and sustenance for the human body is produced by the 
slow oxidation in the tissues of the carbon and hydrogen taken as food. 

This results in the formation of a large amount of carbon dioxide 
and water—the former being carried by the blood to the lungs, where 
it is liberated into the air chambers and then expelled through the 
mouth in the act of breathing. 

For this purpose the average volume of air needed by an adult is 
1,500 gallons per day. 


V. OXIDES 
of the different elements differ in various ways, e.g. state, effect pro- 
duced by heat, solubility in liquids. 

Solids. Lime (calcium oxide), baryta (barium oxide), zinc 
oxide, oxides of iron, magnesium, copper, tin, mercury, lead. 

Liquids. Water (oxide of hydrogen), nitrogen peroxide. 

Gases. Carbon monoxide, carbon dioxide, sulphur dioxide, 
nitrous oxide, nitric oxide, ozone (oxide of oxygen). 

When heated, some evolve oxygen, e.g. mercuric oxide, red lead, 
silver oxide, chromium trioxide, and all peroxides. 

Some do not yield oxygen, e.g. lime, baryta, alumina, sand, zinc 
oxide, water (except at very high temperatures). 

They vary very much in respect to solubility in water and other 
common solvents :— 

Very soluble in water. Phosphorus pentoxide, hydrogen peroxide, 
sulphur trioxide, sodium oxide, potassium oxide. 

_ Moderately soluble in water. Carbon dioxide, sulphur dioxide, 
baryta. 

Slightly soluble in water. Lime, iron oxide. 

Nearly insoluble in water. Lead oxide, sand. 

Soluble in dilute nitric acid. Bismuth, copper, zinc oxides, 
barium peroxide, litharge. 

Insoluble in dilute nitric acid. ‘Tin oxide, antimony trioxide, 
lead peroxide, sand. 

Oxides are usually classified as :-— 

1. Acidic Oxides. Those which combine with the elements of 
water to form acids—e.g. oxides of sulphur, carbon dioxide, oxides 
of nitrogen (usually non-metals). 

2. Basic Oxides. Those which combine with the elements of 
water to form bases (metallic oxides)—e.g. sodium and potassium 
oxides, lime, baryta. 

_ 3. Peroxides—which yield oxygen on Petre and which do not 
react with water to form acids or bases, e.g. manganese dioxide, lead 
peroxide, barium peroxide, hydrogen peroxide. 


5 


SECTION VIII 


I. ACIDS, ALKALIS, BASES, SALTS 


HESE are important classes of compounds which are very 
closely related one to the other. 
Some hundreds of acids are known, nearly a score of — 
alkalis, about 100 bases, and thousands of salts. Each class exhibits cer- 
tain distinctive characteristics by means of which it may be identified. — 
Acids possess a sour taste; change the colour of certain natural 
colours; react with alkalis and bases to produce salts; always 
contain the element hydrogen and conduct electricity in solution. 
It was stated by Lavoisier that oxygen was the real acidifying ~ 
principle, but this has been disproved. ’ 
Alkalis have a caustic taste and a soapy feel; they also change 
certain colours, react with acids to form salts, and as a rule are very 
soluble in water. 
Bases are compounds which neutralize acids to form salts and 
contain a metallic element. : 
Salts are compounds in which the hydrogen of the acid has been 
replaced, partly or entirely, by a metal. They are usually (a) of a 
solid and crystalline nature, (b) neutral to litmus, (c) when in solution 
decomposed by the passage of an electric current. 
Salts may be normal, in which all the replaceable hydrogen has been 
replaced by a metal; acid or hydrogen, in which some has not been 
replaced ; basic, which contain a greater quantity of the metallic 
radicle than is sufficient to replace completely the hydrogen; and 
double, which contain more than one metal. 1 
Copper sulphate, zinc chloride, magnesium chlorides common salt, 
Glauber salt, Epsom salt, sodium carbonate, are examples of normal 
salts; sodium bicarbonate, nitre cake are acid salts; copper car- 
bonate, white lead are basic; and alum is a double salt. q 
Examine samples of the following :— : 
(a) Acids. Acetic, boric, citric, hydrochloric, nitric, oleic, oxalic, 
palmitic, salicylic, stearic, sulphuric, tannic, tartaric. | 
(b) Alkalis. Caustic soda, caustic potash, quicklime, ammonia, 
washing soda, baryta. ; 


66 


ACIDS, ALKALIS, BASES, SALTS 67 


(c) Bases. Metallic oxides such as black copper oxide, litharge, 
zinc oxide, mercuric oxide. 

'To study the action of acids and alkalis on coloured bodies, use 
solutions of the following indicators :— 

(a) Litmus in water. 

(6) Methyl orange in water. 

(c) Phenolphthalein in 50 per cent. alcohol. 

(dq) Lacmoid in 50 per cent. alcohol. 

(e) Congo red on paper. 

(f) Cochineal in 25 per cent. alcohol. 

Note that acids may turn blue litmus to red ; lacmoid to red; 
methyl orange to pink ; cochineal yellowish red ; Congo red to blue. 
Further, certain of these indicators are not affected by certain acids, 
e.g. the fatty acids—oleic, stearic, and palmitic—do not change methyl 
orange. 

Note that alkalis turn litmus and lacmoid to blue; methyl orange 
to yellow ; phenolphthalein to pink ; cochineal to violet. 

Note that bases (other than alkalis), as a rule, have no action on 
indicators. 


Preparation of Salts. When acids and alkalis or bases react, 
a chemical change results, a salt being formed. This is termed neu- 
tralization, e.g.:— — 


1. Take some dilute hydrochloric acid in a dish and add a drop or 
two of litmus. Now add caustic soda, drop by drop, till the litmus is 
just turned purple. Evaporate down to dryness. The residue is 
common salt. 

2. In a similar way neutralize caustic potash with nitric acid and 
obtain solid nitre. 

Salts may be obtained also by the following methods :— 

3. Dissolve copper oxide in hot dilute sulphuric acid, evaporate to 
a small bulk, and cool to crystallize out the copper sulphate. 

4, Dissolve zinc in dilute hydrochloric acid, and concentrate to 
obtain zinc chloride. Note that so long as there is any free acid in this 
solution, Congo red is turned blue, but when entirely neutralized no 
effect is produced on the indicator. 

Salts of hydrochloric acid are called chlorides. 


» nitric a » nitrates. 

,, sulphuric sie ,, sulphates. 
» acetic “A » acetates. 

» citric # »  citrates. 

» carbonic oe ,, carbonates. 
», tartaric “f ,,  tartrates. 


» oxalic a ,, ,  oxalates. 


68 - TEXTILE CHEMISTRY 


Salts of palmitic acid are called palmitates. 
» Oleic a 5 oleates. 
», Phosphoric __,, - phosphates. 


Many salts are without action upon indicators, but some do affect — 
them, e.g. :— 4 

Copper sulphate turns blue litmus red, so does zine chloride, while — 
sodium carbonate turns red litmus blue. : 

Fats may be looked upon as salts (esters they are called) of certain — 
organic acids, of which an enormous number are known. Here the © 
base is glycerine, not a metallic oxide, although metallic oxides will — 
combine with the fatty acids. 

Palm oil is largely a glyceride of palmitic acid. 

Mutton fat contains a large quantity of glycerine stearate. 

Lard contains a considerable amount of glycerine oleate; while — 

Beef fat is a mixture of the glycerides of stearic, oleic, and palmitic — 
acids (chiefly the former). 

Lead plaster is made by boiling olive oil with litharge, and is really i 
lead oleate. 

Compounds of metallic oxides and fatty acids are sometimes 
termed metallic soaps, and their production is often a cause of serious ~ 
trouble during sizing operations if incompatible ingredients have been — 
used in the mixing. 3 

Esters are all hydrolyzed on boiling with caustic alkalis, ie. the — 
glycerine is regenerated and the alkali salt of the fatty acid formed. 
This new salt is called a soap, the process often being termed on that 
account saponification. 

Soft soaps are usually potash soaps, and hard soaps are generally — 
soda soaps, but not always so, as the nature of the fat or oil used has a — 
considerable influence on the physical properties of the soap formed. 


II. SULPHURIC ACID 


It is almost impossible to overrate the great commercial and indus- 
trial importance of this well-known acid. South-west Lancashire and 
North-east Wales are full of factories for its manufacture, and the 
normal annual production of the acid in Great Britain alone is two 
million tons out of four million tons consumed yearly. ; 

It was prepared originally from ferrous sulphate (green vitriol) by 4 
the action of heat, which expelled sulphur trioxide and water vapour, 
that united in the receiver to form the acid and which, being of an oily 
nature, was named oil of vitriol. d 

In the seventeenth century it was prepared by heating sulphur and 
nitre, which can be illustrated by using the apparatus shown in Fig. — 
119. The mixture of sulphur and nitre is gently heated until the 


ACIDS, ALKALIS, BASES, SALTS 69 


sulphur burns in the nitre. Sulphur trioxide distils over and is col- 
lected in the water contained in the bend, thus forming a dilute 
solution of sulphuric acid. 

The first sulphuric acid works was established in Richmond in 1740. 
After that time the industry rapidly extended and the method of 
manufacture was greatly improved. Gay Lussac devised a means of 
trapping the most valuable by-product and Glover invented a method 
for using it over again. 

The cost of manufacture was thus greatly reduced, and the use of 
the acid became much more general. Further reduction in the cost of 
production was effected (but at the expense of purity) by using pyrites 
instead of sulphur to yield the sulphur dioxide. 


The principle of the English method of manufacture is illustrated 
in Fig. 120. 

Sulphur is heated in a hard glass tube through which air is passing. 
This forms sulphur dioxide, which is carried forward with excess of air 
through a flask containing nitric acid, which when warmed liberates 
nitric oxide. The mixture of sulphur dioxide, air and nitric oxide now 
passes to the large boiling-tube, where it meets with steam, with the 
result that sulphuric acid is produced and falls to the bottom of the 
tube. 

The nitric oxide acts as the agent which brings about the change, 
and is not itself used up. If the gases from the tube are passed through 


70 TEXTILE CHEMISTRY 


a flask containing strong sulphuric acid, the nitric oxide will be 
absorbed and not lost to the process. It can be used over again 
by putting the liquid into the flask which contains the nitric acid. 

These flasks correspond to the Glover and Gay Lussac towers in 
the manufacturing plant, details of which can be obtained from the 
larger chemistry textbooks. 

The current through the apparatus is maintained by running water 
from the aspirator. 

The Contact Process for the manufacture of sulphuric acid: 
The purest and strongest acid is now made by a catalytic contact 
process, on the perfecting of which enormous sums of money and much 
labour and research have been expended. 

The laboratory method of working is simple to carry out and easy 
to understand (Fig. 121), but on the manufacturing scale it is much 
more difficult to accomplish successfully. 

A catalyst is a substance which acts as an accelerator of a chemical 
change. The precise action is not definitely known. Ostwald com- 
pares it to a “chemical oil.” Manganese dioxide and cobalt oxide 
both act as catalysts in the preparation of oxygen from potassium 
chlorate and bleaching powder respectively. 


Bigaics 


The contact process has been worked principally on the Continent 
for the production of an acid which was necessary to the dye industry, — 
and which could not be produced by the English chamber process. — 
There is no doubt but that it will ultimately displace the older method, — 
particularly as during the last few years other catalytic agents besides — 
platinum have been used successfully. 4 

For the experimental illustration oxygen gas from an aspirator a 
O and sulphur dioxide from a siphon §S are forced through strong sul- 
phuric acid in a bottle D, to dry them. They are then passed over — 
gently heated platinized asbestos in a hard glass tube P. Here they © 
combine to form sulphur trioxide, which is led into water W, thereby — 
forming sulphuric acid. ; 


4 


ACIDS, ALKALIS, BASES, SALTS 71 


Sulphuric acid comes into the market in various strengths, usually 
packed in carboys (Fig. 79, page 30). 

Chamber acid has a strength of 62 per cent. to 70 per cent. and is 
used for making salt cake and fertilizers. Its sp. gr. is about 1-6. An 
acid of 78 per cent. to 80 per cent. is used for many technical purposes, 
including the manufacture of superphosphate. Its sp. gr. is about 
1-72. This is collected at the foot of the Glover tower. 

Double oil of vitriol (D.O.V.) has asp. gr. up to 1-84 and a strength 
between 93°5 per cent. and 98-3 per cent. The impure acid is often 
termed brown oil of vitriol (B.O.V.), due to its colour (sp. gr. 1-72). 

“Commercial ” acid will always contain impurities such as iron, 
arsenic, lead, and copper. It should never be used in the preparation 
of food-stuffs or drugs. 

By the contact process a pure acid is produced of 100 per cent. 
strength, and besides this, sulphur trioxide is dissolved in it to give 
fuming sulphuric acid containing sometimes as much as 45 per cent. 
excess of the trioxide. This is used chiefly for the production of 
intermediate products for the manufacture of dye-stuffs. 

Strong sulphuric acid, when mixed with water, produces an enor- 
mous amount of heat; on this account the acid should always be 
added to water, and not water to acid. Its great affinity for water can 
be shown in various ways, e.g. Expose a weighed dish of it to air and 
weigh again after several hours; it will have increased considerably, 
and have become weaker. Add some to a little starch or sugar; it is 
dehydrated, leaving a black mass of carbon. 

The test for the identification of sulphuric acid is to add a few drops 
of nitric acid and then a solution of barium nitrate. If a white pre- 
cipitate is produced, the acid or one of its salts is present. 

The use of barium chloride is not suitable in the presence of lead, 
which sulphuric acid is always liable to contain. 

Uses.——Among the enormous number of uses to which sulphuric 
acid is put, some of the most important are: Manufacture of chemi- 
cals such as sodium carbonate, hydrochloric acid, nitric acid, alum, 
phosphorus ; of explosives of all kinds ; of fertilizers, such as sulphate 
of ammonia; of superphosphate ; of artificial silk; in the dyeing, 
bleaching, and electroplating industries. 


Ill. NITRIC ACID 
or aqua fortis (which means strong water) was known to the alchemists 
and was largely used for dissolving metals, nearly all of them being 
soluble in it. 

It is a compound containing 1-6 per cent. hydrogen, 22-2 per cent. 
nitrogen, and 76-2 per cent. oxygen. Like sulphuric acid it has an 
enormous industrial application. 


72 TEXTILE CHEMISTRY 


PREPARATION | 

1. From nitre or saltpetre and sulphuric acid. Nitre is potassium 
nitrate. When it is heated with strong sulphuric acid it is decomposed, 
nitric acid being liberated as a gas. If this gas is cooled it condenses 
to liquid nitric acid. On a small or laboratory scale the operation is 
usually performed as shown in Fig. 122, which should require no 
further explanation. 

2. From Chile saltpetre and sulphuric acid. Nitre is too expensive 
and too rare to use on the commercial scale. Therefore the cheaper 


x (fe cake 


sodium nitrate is used in its place, and instead of glass vessels, iron 
retorts and porcelain bottles are employed. 

Fig. 123 shows in section the usual English plant. A more modern — 
retort, which is in use in America, is shown in Fig. 124. At the end — 
of the condensing bottles a tower filled with coke is sometimes placed, 
down which trickles water. This absorbs the last trace of nitric acid, 
which would otherwise escape into the air. ; 

The chemicals used are Chile nitre which has been purified until it — 


ACIDS, ALKALIS, BASES, SALTS 73 


contains 98 per cent. to 99 per cent. of sodium nitrate and is free from 
sodium chloride, and sulphuric acid of sp. gr. 1-7. 

These will give a nitric acid up to a sp. gr. of 1-38. For stronger 
acid, a stronger sample of sulphuric acid must be used. 

The reaction between moderately hot sulphuric acid and sodium 
nitrate results in the production of nitric acid and sodium hydrogen 
sulphate. 

If the temperature be increased further, more nitric acid would be 
liberated with the production of sodium sulphate (salt cake or Glauber 
salt), but the manufacturer finds that the high temperature at which 
the operation must be conducted results in the decomposition of a 
large quantity of the nitric acid thereby produced. 

Consequently it is usual to stop at the first reaction, and the 
chemical which is drawn from the retort is sodium hydrogen sulphate 
—technically known as nitre cake. 

Nitre cake can be used instead of sulphuric acid in certain industrial 
applications, e.g. bleaching, the manufacture of baking powder, etc. 
(See Partington, “ Industrial Chem.,”’ pages 161, 162 ; or “J.8.C.L.,” 35, 
857, 1916; or “Chem. Tr. Journ.,’”’ 1916, 28, 109, 393, for full lists.) 

3. From the air. The beds of natural nitrates in India, Chile, 
Egypt, etc., are being exhausted rapidly, and nearly twenty-five years 
ago Sir William Crookes suggested the inexhaustible air as a source of 
supply. 

When a mixture of oxygen and nitrogen is “ sparked ”’ electrically 
under certain conditions it produces oxides of nitrogen which, dissolved 
in water, form nitric acid (Cavendish’s discovery). Crookes showed 
that air can be burned to nitric and nitrous acids in a powerful electric 
are. 

There are now several successful schemes for applying these facts 
to the commercial production of nitric acid and calcium nitrate. It is 
carried out in Norway (Norwegian saltpetre) by the Birkeland and 
EKyde method, in which a large flame, produced by a current of high 
voltage, is spread over copper-surface electrodes by the action of an 
electromagnet, the current alternating fifty times per second. 

The nitric oxide produced is rapidly cooled and then combined with 
oxygen to form nitrogen peroxide, which is afterwards absorbed by 
water to form nitric acid, or by lime to form nitrate of lime. 

During the Great War, Germany rapidly developed this and other 
methods until she was no longer dependent upon the natural nitre beds 
for the production of nitric acid, but obtained it all from the air. 

Commercial nitric acid can be purified by redistillation with sul- 
phuric acid in glass vessels, and the brown colour, which is due to nitric 
_ oxide dissolved in the liquid, removed by warming the acid to 70° C. 
and passing a current of carbon dioxide through it (Fig. 125). 


74 TEXTILE CHEMISTRY 


Chemically pure acid is made by either :— 

1. Using perfectly pure materials, or 

2. Treating commercial acid with barium nitrate (to precipitate 
sulphuric acid) and silver nitrate (to precipitate chlorine and hydro- 
chloric acid), and then redistilling with pure sulphuric acid at a low 
temperature. 


PROPERTIES 


A colourless liquid of sp. gr. varying from 1-29 (46 per cent.) to 1-41 
(67-5 per cent., ordinary conc.) and 1-53 (100 per cent.). 

The sp. gr. is best determined with an hydrometer (see page 
29), or by using a Joly balance (see pages 29, 30). 

Boiling-point, 86° C. 


oe 


Warm x Sikes 
a. 


Fig.126 
F1G.125 Es 


Very active oxidizing agent—many interesting experiments can be — 


performed to illustrate this property :— j 
1. Put some warm dry sawdust on a porcelain tray in a fume ~ 
chamber, add some strong nitric acid and stir. Dense fumes of nitric 
oxide are evolved and the mass will in all probability burst into flame. 
2. Place a small crucible on sand in the bottom of a wide beaker, — 
and in the crucible put a few c.c. of a mixture of equal parts of strong — 
nitric and strong sulphuric acids. 
By means of a long tube drawn out to a jet, allow drops of turpen- 
tine to fall into the crucible. The turpentine is immediately oxidized 
and bursts into flame. 
3. Put 2 grams of sugar in a large test tube, add 5 c.c. of strong 


nitric acid and warm. The sugar is oxidized to oxalic acid, which can — 


be obtained by crystallization. | 
Conduct this eet in a fume chamber or out of doors on | 


ACIDS, ALKALIS, BASES, SALTS 75 


account of the dense fumes of the deadly oxides of nitrogen that are 
evolved. 

4. Drop a few c.c. of the strong acid on a lump of metallic tin. Itis 
converted into white tin oxide. 

5. Take a small wide-mouth flask, put in it some nitre and conc. 
sulphuric acid, and gently heat it on a sand bath (Fig. 126). As soon 
as the flask is full of nitric acid vapour, drop in 1 c.c. of carbon disul- 
phide, and immediately apply a light to the mouth of the flask. The 
carbon disulphide burns with a bright blue flame. 

It is an intensely strong acid, e.g. add a drop of acid on the end of 
a glass rod to a litre of water, the solution will turn blue litmus red ; 
Congo red, blue; and methyl orange, pink. 

It has a very pronounced and often corrosive action on organic 
matter, e.g. :— 

1. A feather is made yellow and destroyed if dipped in it. 

2. It turns flour yellow. This can be used as a test to distinguish 
between pure starch and wheat or other flour. The experiment should 
be made in a white basin or dish. 

3. It stains the fingers yellow and produces a similar effect on 
other bodies, e.g. indigo, proteids, silk. 

In the case of silk, we can produce a permanent orange colour on it 
if it be soaked first in dilute nitric acid and then in ammonia solution. 
This is sometimes called the Xanthoproteic Reaction. 

The test for the identification of nitric acid is its action on a cold 
strong solution of ferrous sulphate, which is turned black by it. The 
black substance is decomposed on heating. A nitrate will give the 
same reaction if it is first treated with strong sulphuric acid. 


USES OF NITRIC ACID 


1. In the preparation of gun-cotton. Make a mixture of equal 
volumes of strong nitric and strong sulphuric acids. Immerse in it for 
fifteen minutes small tufts of cotton wool. Remove with a glass rod 
and wash free from acid. Dry in air. 

It is very inflammable ; burn a small piece on a filter paper, and if 
it has been properly prepared it will burn away without igniting the 
paper. 

2. In the manufacture of nitro-glycerine and dynamite, blasting 
gelatine, cordite, smokeless powders, etc. 

3. For the production of T.N.T. (which is made by nitrating 
toluene), and of nitro-benzene, sometimes called oil of mirbane, used 
as a deodorizer in certain textile preparations and as artificial almond 
flavouring. 

4. For the preparation of picric acid, which is made from phenol 
(carbolic acid) and nitric acid. 


76 TEXTILE CHEMISTRY 


5. In the manufacture of Chardonnet artificial silk, celluloid, etc. 

6. For the preparation, of nitrates, such as silver nitrate (used in 
photography, pharmacy, for mirrors, marking ink, etc.) ; ammonium 
nitrate (used in the newer explosives) ; strontium nitrate (red fire) ; 
barium nitrate (green fire). 

7. As a pickling or cleansing liquor for copper. 

8. In the manufacture of dextrine from starch, and of dyes from 
coal-tar products. 


TIG. 127 


IV. HYDROCHLORIC ACID, 


also known as muriatic acid and spirits of salt, is made foe common ~ 
salt by heating with moderately strong sulphuric acid. 

Fit up the apparatus shown in Fig. 127. In the flask put some 
rock salt and a little water. Add strong sulphuric acid through the ~ 
thistle funnel. Hydrochloric acid gas will be evolved, at first without — 
heat, and may be collected in the gas jar. 

Fill several jars ; then attach a filter funnel to the end of the tube, 
and collect some of the gas in water placed in an evaporating dish. It — 


ACIDS, ALKALIS, BASES, SALTS 17 


will be necessary to heat the mixture in the flask towards the end of 
the experiment. 

With the gas perform the following experiments :— 

1. Test its combustibility, and also if it will support combustion. 

2. Note that it fumes in air, and much more so when in contact with 
a drop of strong ammonia solution held on the end of a glass rod. 

3. Test its action on litmus paper and Congo red paper. 

4. Test its solubility in water by inverting a jar in a pneumatic 
trough half full of water. 

Also test with litmus paper, and with a solution of silver nitrate, 
the water through which the gas has been passed. A white precipitate 
will be produced with silver nitrate if hydrochloric acid is present. 

Hydrochloric acid comes into commerce as a solution in water 
usually of about 32 per cent. strength (sp. gr. about 1-16), which can 
be diluted as required. 


SS 


Cee 


On the industrial scale the flask is replaced by an iron pot and the 
heating is done in two stages in a double furnace. Fig. 128 is a sketch 
of the plant used. 

Salt and sulphuric acid are heated first in the pot A, and the gas 
evolved passes by means of the pipe B to the towers C, which are filled 
with coke, and down which a stream of water trickles. The solution 
of hydrochloric acid is drawn off at the bottom. 

In the second stage the damper D is opened, the contents of A 
raked into the furnace E, which is heated from a coke fire at F. The 
gas again passes into the pipe B by means of G, and so to the collecting 
towers. The residue in E is called salt cake, and is chiefly sodium 
sulphate. 

Hydrochloric acid is used in the manufacture of chlorine, and for 
making chlorides, and in calico-printing, bleaching, dyeing, etc. 


EXERCISES 
Prepare (a) zinc chloride by dissolving zinc in hydrochloric acid ; 


78 TEXTILE CHEMISTRY 


(6) magnesium chloride by dissolving magnesia in the acid ; (c) calcium 
chloride by dissolving chalk in it. 

Test the solubility of the following metals and oxides in dilute and 
in strong acid: Copper and copper oxide, iron and iron rust, lead and ~ 
litharge, mercury and mercuric oxide. 


V. AMMONIA 

Sal-ammoniac (meaning a salt of ammonia) was first prepared by 
the Arabs centuries ago, by heating camel refuse in or near the temple 
of Jupiter Ammon, in the Libyan Desert, and so received its name 
from that building. 

The gas itself is called ammonia or volatile alkali, and can be 
obtained easily from sal-ammoniac by heating it with lime or caustic __ 
soda (Fig. 129). It was formerly obtained by heating horn, and so 
received the name “spirits of hartshorn.” 


~ Gauze Collar 


At the present day an important source of our ammonia supply is — 
gas liquor. When coal is distilled at gasworks, a large quantity of — 
ammonia is evolved, which is collected by solution in water. This solu- — 
tion is known as ammoniacal, or simply gas, liquor. The liquid is mixed — 
with quicklime and gently heated, the ammonia which is evolved being — 
led by means of pipes into acid—either sulphuric to make sulphate of — 
ammonia, or hydrochloric, to make sal-ammoniac or ammonium chloride. — 

An enormous amount of ammonia is now prepared synthetically — 
from hydrogen and nitrogen. From this source it is entirely free from — 
coal-tar products. a 

Ammonia is usually supplied in commerce as a strong solution in — 


water. From this the dry gas may be obtained by using the apparatus 
shown in | Figs. 130 and 131. Z 


PROPERTIES . e- 
Very pungent odour, colourless, caustic taste, turns red litmus blue, 


fumes in contact with hydrochloric acid gas, due to formation of solid — 
ammonium chloride. q 


ACIDS, ALKALIS, BASES, SALTS 79 


Of all gases it is the most soluble in water—the solution is called 
ammonium hydrate. At ordinary temperatures 1 volume of water 
will dissolve between 700 and 800 volumes of ammonia. The solution 
is attended by considerable increase in volume, and decrease in density, 
so that strong ammonia has a sp. gr. of 0-88. Fig. 66, page 18, shows 
the apparatus usually used to illustrate the great solubility of am- 
monia in water. 

It is a very light gas, being only slightly more than half as heavy as 
air. It is fairly easily condensed to a liquid which has a considerable 
industrial application as a refrigerating agent for the production of 
blocks of ice. 

Ammonia does not burn in air, but if it is first mixed with oxygen 
it will do so, producing a greenish yellow flame. Fig. 132 illustrates 
a form of apparatus which can be used. 


Ammonia is used for neutralizing acids in dye-stufis; by dyers 
when milder alkali than soda is needed or when volatility is desired ; 
in the manufacture of Turkey red oil; as a fixing agent for certain 
metallic mordants. 

Ammonium chloride is used for aniline blacks, and ammonium 
carbonate (sal volatile), which may be prepared by heating ammonium 
sulphate with chalk and collecting the sublimate, is used as a substitute 
for dunging in dyeing Turkey reds. 

Ammonium acetate, made by mixing equivalent quantities of 
ammonia and acetic acid, is used with alizarines, and as a stripping 
agent for dyed wool and silk. 

Ammonium oxalate is sometimes used in wool-dyeing. 


SECTION IX 
THE ELEMENTS OF CHEMICAL THEORY 


I. THE ATOMIC THEORY 


HAT the ultimate constitution of matter is, will probably — 
: N | never be thoroughly known; but that does not prevent — 
speculation upon the point. Ideas of this kind are called — 
theories, and the one accepted at the present day is that proposed by 
Dalton, who adapted it in 1808 from an ancient Greek idea. . 
The main principle of it is that matter is not infinitely divisible— _ 
that ultimately a point is reached beyond which it is impossible to — 
divide up the substance by any physical or chemical operations. We 
then reach a small particle called the atom. | 
There is very little direct proof of the truth of this theory, and it 
might at any time have to be abandoned, should newly discovered © 
facts oppose it, but at the present time it is accepted for many reasons 
that will appear as the study of chemistry is continued. | 
By this theory atoms are assumed to be :— 
1. Elementary in their nature. Therefore there can be only the 
same number of sorts as there are elements. 
2. Endowed with a mutual attractive force called chemical affinity 
or attraction, by virtue of which, when brought into intimate contact, — 
they combine with one another. This chemical affinity varies with the — 
kind of atom. a 
3. Absolutely indestructible. 
4. (If of the same kind) Of equal mass and alike in all respects. 
Note.—Nothing is said about the shape of an atom, nor the size. 
Dalton originally used certain symbols to denote them, such as © for 
oxygen, © for nitrogen, © for hydrogen, @ for carbon, @ for sulphur, — 
@ for phosphorus, etc., and hence the idea arose that they were thought — 
to be spherical. . ; 
From assumption 2 (above), it is apparent that we shall often have — 
aggregations or groups of atoms. These are known as Molecules. 
Molecules may be made up of atoms all of the same kind, in which case — 


80 


THE ELEMENTS OF CHEMICAL THEORY 81 


we have elements, or different kinds of atoms may unite, forming 
compounds. 

A molecule may be defined as the smallest mass of any element or 
compound which can be supposed to exist alone and have all the 
properties of that element or compound. 

As a rule, molecules of elements consist of two or more atoms ; the 
exceptions are zinc, potassium, sodium, cadmium, mercury (one atom 
each) ; arsenic, phosphorus (four atoms); ozone (three atoms). 

Molecules of compounds do not contain a very large number of 
atoms—seldom more than ten. The exceptions are the compounds of 
carbon, which sometimes contain hundreds, e.g. starch is thought to 
have 4,200 atoms per molecule. 

The atomic theory’s best bulwark is the support given it by the 
laws of chemical combination, which are completely explained by it ; 
in fact, it was from a careful study of two of them that Dalton was led 
to formulate it. 


II. ATOMIC AND MOLECULAR WEIGHTS 


We shall here consider what is meant by atomic and molecular 
weights. The methods by which they may be determined are too 
difficult for beginners to follow. 

As an atom is so small, it is of course utterly impossible to weigh 
one directly ; therefore the mass is given relatively, and originally the 
number which denoted the atomic weight of an element expressed the 
number of times it was as heavy as one atom of hydrogen. 

It was found that one atom of oxygen was nearly sixteen times as 
heavy as one atom of hydrogen. Now in practice it is much easier to 
experimentally determine atomic weights with reference to oxygen 
rather than hydrogen. And if ;; of the atomic weight of oxygen be 
considered as unity, the atomic weight of hydrogen becomes 1-008 
instead of 1. This system of calculation is the one adopted in the 
International Table of Atomic Weights. 

For all elementary purposes the variation is negligible. 


List of Approximate Atomic Weights of the Commoner Elements 


Metals 
Beuwumm = fo 5... OT Magnesium . . . . 244 
Settee er. ek. «137 Manganese . . . . 59 
On ae ea: 4 dletoury Go 2 BS Se ee) 
Beracuucgic, C.D Potassiim:  .. ». =7 > 2a 
Beever, =. 1 t& «. . 64 Silvéetes) oa). eS 
Peeks | | «56 Soditim: ©. =.) (ae eee 
i ee ee 1 Titi 2 Soka 2 
pene ee RO Ge ew 2 ORG 


6 


82 TEXTILE CHEMISTRY 


Non-metals 
Boron aera aie forges 2) Hydrogen 4... 220eeame 1 
Bromine) 24 Nas oe Iodine . 3 
Carbon Feats MEE ek ae Nitrogen © <7) 2) (eee 14 
Chiorine 40) p03y) 4 ee OO eee wee oo A 
ACORN 2a 2 ve ae ee Fe 4 
POUT HAr 2 eee nee Ba 


By the molecular weight is meant the number of times the molecule 
of an element or compound is as heavy as one atom of hydrogen or yg 
of one atom of oxygen. 

For elements that contain two atoms, this will be twice the atomic — 
weight. For compounds it is the sum of the weights of all the atoms 
in the molecule. 


II. THE LAWS OF CHEMICAL COMBINATION 


Scientific laws are not made—they are discovered. ‘Their applica- 
tion is the opposite to “‘ man-made laws.” 

If the individual breaks the law of the land, he is penalized—in other 
words, the individual has to conform to the law. In science the law — 
has to conform to individual experiment. Should experimental work — 
fail to agree with the law, the law is assumed to be stated wrongly. 

The following laws have, so far, never been contradicted by accurate _ 
experiment, but have been confirmed in thousands of instances. 

1. Proust’s Law of Constant (or fixed, or definite) Proportion. 
The same compound always contains the same elements united 
together in exactly the same proportion by weight. 

E.g. calcium carbonate, whether it occurs as chalk, or Iceland spar, — 
or calcite, or marble, or aragonite, or egg shell, or oyster shell, always — 
contains in 100 grams of it 40 of calcium, 12 of carbon, and 48 of — 
oxygen. A 

Magnesium oxide, whether made by heating magnesium in air or — 
by ignition of the nitrate or carbonate, or in any other way, always — 
consists of 24 parts of magnesium to 16 of oxygen. 

2. Dalton’s Law of Multiple Proportions. When the same two 
elements combine together to form more than one compound, the — 
proportions by weight in the other compounds are always some simple — 
multiple of the proportion found in the simplest compound, § 

E.g. Hydrogen and oxygen unite to form two compounds, (a) 
water, in which the ratio of hydrogen to oxygen is 1 to 8, and (0) 
hydrogen peroxide, in which the ratio is 1 to 16 (8x 2). q 

Copper and sulphur unite to form two sulphides in which the pro- 7 
portion of copper and sulphur are respectively 64: 32 and 128:32. 

Nitrogen and oxygen form a series of compounds—the oxides of - 


THE ELEMENTS OF CHEMICAL THEORY 83 


nitrogen—in which the following proportions of nitrogen and oxygen 
are found :— 


Nitrous oxide : . 28:16, ie. 28:16 

Nitric as See Sastre ae LO ke 
Nitrogen trioxide . owas 3. 2a lO oo 
Nitrogen peroxide . , 25704 , 28:16 4 
Nitrogen pentoxide Sie eb tell Baur le eis itp as 


This phenomenon i is quite explicable if we imagine the respective 
elenients “ moving about ”’ in certain definite entities, such as atoms. 

3. Richter’s Law of Reciprocal (or equivalent) Proportions. 
When two different elements unite with the same quantity of a third 
element, the proportions in which they do so will be the same as, or 
some simple multiple of, the proportions in which they unite with each 
other. 

This is best illustrated by a diagram. Let A, B, C represent 
respectively three elements. Suppose B combines with A in the 


: Hy drogen 
VA ot os "Sulphide 


Bi4 16C aS 


BoC 
14 16 C Carbon sisi Duadenad 64 


Fig.133 Figis+ 


proportion 14:1; and suppose C also combines with A in the propor- 
tion 16:1. (Note same quantity of A.) 

Then B will combine with C in the proportion 14:16, or some 
simple multiple of this proportion (Fig. 133), e.g. in marsh gas 12 parts 
of carbon are combined with 4 of hydrogen. In sulphuretted hydrogen 
64 parts of sulphur are combined with 4 of hydrogen ; and we find in 
carbon disulphide that 12 parts of carbon are combined with 64 of 
sulphur—which supports the truth of the Law of Reciprocal A 
tions (Fig. 134). 


_ EXPERIMENTS ILLUSTRATING THE Laws or CHEMICAL COMBINATION 
1. To determine the Composition of Magnesiwm Oxide made in 
Three Ways. Weigh very accurately three pieces of bright magnesium 
ribbon. Each piece should weigh at least 0-1 gram, but not more 
than 0-2 gram. ‘Treat as follows : 


84 TEXTILE CHEMISTRY 


Piece No.1. Put it in a weighed porcelain crucible and heat it over 
a hot flame until it burns and is completely converted into white 
magnesium oxide. Prevent the escape of any of the light powder by 
holding the lid at an angle just above the top of the crucible, using the __ 
tongs. Let the vessel cool and then weigh. ‘The increase in weight 
represents oxygen which has combined with metal to form the oxide. 

Piece No. 2. Put this in a small weighed evaporating basin, and, 
after covering with a watch-glass to prevent loss during solution, add 
two or three drops of dilute nitric acid. Repeat until the metal is 
dissolved. Put the dish on a water bath, and when all the water has — 
evaporated, heat over a hot flame until the magnesium nitrate is com- __ 
pletely converted into the oxide. N.B.—Magnesium nitrate fuses 
when heated, and decomposes with liberation of nitric oxide to pro- 
duce infusible white magnesium oxide. Weigh dish and contents, 
and calculate the proportion of oxygen to magnesium in this sample. 


Piece No.3. Put this in a small beaker and again dissolve in nitric 2 : 
acid ; dilute this solution with a few c.c. of water and then add sodium 


carbonate solution to produce magnesium carbonate. Filter to collect — 
the precipitate on filter paper and dry over a small flame. “4 

When dry, transfer it to a weighed crucible, and heat very strongly — 
until the carbonate is again converted into the oxide. N.B.—The ~ 
carbonate loses weight on heating, the oxide does not. ’ 


Carefully tabulate the results you obtain, showing clearly the © | 


proportion of oxygen to magnesium in each sample, expressing the — 
quantity as per cent. oxygen and per cent. magnesium in each case. 

2. To determine the Relationship between the Proportions in which — 
Oxygen unites with Lead to form Lead Peroxide and LIntharge. q 

Weigh a crucible and put in it a few grams of lead peroxide, care- — 
fully determining its weight. Heat this gently over a small flame, © 
stirring at intervals with a small piece of iron wire until it is converted © 
into litharge. a 

Take care that it does not fuse. N.B.—Litharge is buff in colour. — 
Find the loss in weight—which represents the first portion of oxygen 
liberated. 

After weighing add a few pieces of solid potassium cyanide, put 
the lid on and fuse up the mixture. Ultimately a button of molten 
lead will be formed in the bottom of the crucible. Cool, wash out all 
the soluble salts, dry, and weigh. Find the second loss due to oxygen, 
and compare the two results. N.B.—Potassium cyanide is a deadly 
poison (a salt of prussic acid); therefore take the greatest pre- 
cautions in handling it. 7 

3. Compare the Proportions of Sulphur and Copper in Compe 
Sulphide. 


Make one sample by dissolving a weighed amount of copper in 


THE ELEMENTS OF CHEMICAL THEORY 85 


nitric acid, and precipitating the sulphide with excess of ammonium 
sulphide, filtering, drying, and weighing. 

Make the other sample from pure precipitated copper by heating 
gently in a crucible with flowers of sulphur. The cake formed should 
be broken up several times, and a little more sulphur added each time. 
Finally, the excess sulphur should be very carefully burnt off with the 
lid of the crucible removed. 


IV. THE LAW OF GASEOUS VOLUMES (Gay Lussac) 


(which must not be confused with the physical law relating to expan- 
sion of gases, known as the Law of Charles or Gay Lussac). 

When chemical action takes place between gases, either elementary 
or compound, the volume of the gaseous product bears a simple 
relation to the volumes of the reacting gases, e.g. :— 

1 volume of hydrogen unites with 1 volume of chlorine to form 2 
volumes of hydrogen chloride. 

1 volume of nitrogen unites with 3 volumes of hydrogen to form 2 
volumes of ammonia. 

1 volume of oxygen unites with 2 volumes of carbon monoxide to form 
2 volumes of carbon dioxide. 

2 volumes of hydrogen unite with 1 volume of oxygen to form 2 
volumes of steam, 

etc. 

These are often called two-volume formula gases. 

A “two-volume formula” is generally written [7]. Thus 
(J of hydrogen, (J of chlorine = [7] of hydrogen chloride. 
[1] of nitrogen, (] C1] of hydrogen = [7] of ammonia. 

By examining these expressions we can arrive at the relationship 
between the original and resulting volumes of the reacting gases. 

N.B.—This notation must not be used for solids, e.g. this is wrong : 

(1) of carbon, [7] of oxygen = [7] of carbon dioxide. 

In common language we may sum up the law as follows: 
‘“‘ Gases always combine in equal bulks or 1 part by bulk of one with 
2 or 3 parts of the other.” 


EXPERIMENTAL METHODS FOR DEMONSTRATING THIS RELATIONSHIP 
FOR SOME OF THE COMMONER GASES 


1. To show that 2 Volumes of Hydrogen unite with 1 Volume of Oxygen 
to form 2 Volumes of Steam. 

Fit up the graduated eudiometer tube surrounded with a jacket 

as shown in Fig. 135. Pass in hydrogen until it fills two graduations, 

when the pressure is equal in each limb of the eudiometer. Now add 

oxygen till the third graduation is reached. Circulate steam (or, 

better, amyl alcohol vapour) until the gases are heated to at least 


86 TEXTILE CHEMISTRY 


100° C. and again adjust the pressure. The volume of gas has in- 
creased ; mark this position on the outside of the jacket. Put a screw 
clip on the rubber tube connecting the eudiometer with the levelling 
tube, and then “ spark ” the gas, taking care to first cover the appara- 
tus with a thick duster in case the tube bursts. 

Unscrew the clip and adjust the pressure. It will be found that 
the volume now occupied by the steam will be two-thirds of the 


Sol® Water 


at? 
Mercury £1g.436 


volume occupied by the mixed gases just before the spark was passed. — 
2. To show that 1 Volume of Hydrogen combines with 1 Volume of — 
Chlorine to form 2 Volumes of Hydrogen Chloride. a 
For this experiment, two glass bulbs with side tubes are required — 
filled with the mixed gases obtained by the electrolysis of strong hydro- — 
chloric acid. It is desirable, although not essential, that each side — 
tube be provided with a glass tap (Fig. 136). 3 
One of them (say A) is wrapped in red paper and put away in @ © 


THE ELEMENTS OF CHEMICAL THEORY 87 


dark cupboard and the other is exposed to diffused daylight, but not 
sunlight, for several days until all green colour has disappeared. The 
bulbs are placed over separate vessels containing mercury, into which 
the end of one of the side tubes is made to dip, and the tap on this tube 
is opened. It will be found that the result in each case is the same, 
namely, no gas comes out of the bulb and no mercury passes into it ; 
the volumes of original gas and resulting gas are thus identical. 

On the top of the mercury in the vessel under A is put a solution of 
potassium iodide, and the end of the tube is raised until it reaches 
this liquid. The solution commences to rise because it dissolves the 
free chlorine. When it exactly half fills the bulb, it stops. If the 
bulb be now transferred to a deeper vessel, depressed in it, and the top 
tap opened, the gas expelled will be found to be all hydrogen. 

In the vessel under B should be put water, and on bringing the end 
of its tube in contact with this liquid, it will be found that all the gas 
is soluble in it, i.e. it is all hydrochloric acid gas. If the capacity of a 
bulb be called 2 volumes, half the capacity will count as 1 volume, 
from which we obtain the relationship 1 volume of hydrogen combines 
with 1 volume of chlorine to form 2 volumes of hydrogen chloride. 

3. Z'o show that 1 Volume of Nitrogen combines with 3 Volumes of 
Hydrogen to form 2 Volumes of Ammonia. 

For this demonstration we assume the truth of the value obtained 
in the previous experiment, namely, that hydrogen and chlorine 
combine in equal volumes. 

A tube about a yard in length is required, provided with a well- 
fitting rubber stopper through which passes a dropping funnel with a 
well-ground glass tap (Fig. 137). 

The stopper is removed and the tube completely filled with chlorine. 
This is best done over strong brine. The stopper is reinserted and 
strong ammonia solution put into the funnel. The tap is very carefully 
turned and a few drops of the liquid allowed to enter the tube. 

The ammonia is immediately decomposed by the chlorine to form 
hydrochloric acid with liberation of nitrogen, the energy of combina- 
tion being sufficient with the first two or three drops to produce flashes 
of light. A little more ammonia is run in and the tube inverted 
several times until all the chlorine is used. Dilute sulphuric acid is 
now put into the funnel and run into the tube. This neutralizes the 
excess of ammonia, and dissolves the ammonium chloride crystals that 
have also been formed. Water is then allowed to enter until the tube 
is full of liquid and gas, which will be so when a bubble of gas attempts 
to pass up through the funnel. 

The gas left in the tube is measured and compared with the volume 
of chlorine used. The result will be as 1 isto 3. The residual gas can 
now be proved to be nitrogen, and as 3 volumes of hydrogen were 


88 TEXTILE CHEMISTRY 


required to satisfy 3 volumes of chlorine, the ratio of nitrogen to 
hydrogen in ammonia must be | to 3. 

4. To show that Carbon Dioxide and Sulphur Dioxide each contains 
its own Volume of Oxygen. 

A small flask is fitted with a tight-fitting rubber stopper through 
which pass two copper rods and a glass tube. To the ends of the 
former, which are to be put inside the flask, is attached a spiral of thin 
platinum wire. The glass tube is bent into the form of a double right- 
angled bend, for use with a manometric tube (Fig. 138). 


F1G.137 


FIG.139 


A small piece of charcoal or sulphur is put in the spiral, the flask _ 
filled with oxygen (by means of a tube not shown in the figure), and — 
the level of mercury in the manometer tube is marked. The ends of © 
the copper rods are connected to the terminals of a suitable battery — 
and a current of electricity is passed through, with the result that — 
the platinum becomes red-hot, which heats the carbon or sulphur — 
sufficiently to make it burn to carbon dioxide or sulphur dioxide. _ 

Due to the heating effect, the volume of gas is increased, but when — 
it is allowed to cool down to the original temperature, it is found that 
the final volume is the same as the original. In other words carbon ~ 
dioxide or sulphur dioxide contains its own volume of oxygen. 


e 


THE ELEMENTS OF CHEMICAL THEORY 89 


5. T'o show that Nitrous Oxide contains an equal Volume of Oxygen, 
Nitric Oxide half its Volume of Oxygen, and Sulphuretted Hydrogen its 
own Volume of Hydrogen. 

For all these determinations the same piece of apparatus can be 
used—known as a “thumb tube” (Fig. 139). 

It is filled with one of these gases and put over a vessel containing 
mercury, the level of which is marked on the tube. A small pellet 
of metal (potassium for the oxides of nitrogen, and tin for sulphuretted 
hydrogen) is pushed under the surface of the mercury in the dish and 
allowed to rise to the surface of the mercury in the tube. 

The finger is then put under the end of the tube and the pellet 
jerked into the horizontal portion. This is then carefully heated. 
The potassium combines with the oxygen in the oxides of nitrogen, 
liberating nitrogen ; and the tin decomposes the sulphuretted hydro- 
gen, forming tin sulphide and liberating hydrogen. 

The gas is allowed to cool and the level of mercury compared with 
the original, from which the ratios will be found to be as that stated 
above. 


V. AVOGADRO’S LAW 


states that “‘ equal volumes of all gases under the same conditions of 
temperature and pressure contain the same number of molecules.”’ 
This law is now admitted to be as true as the other four, but its 
proof is beyond the requirements of a student of elementary chemistry, 
as it requires more than an elementary knowledge of mathematics 
and physics. 
At this stage it must be accepted. 


EQUIVALENTS 

When chemical reaction occurs between certain substances, notably 
acids and metals, it is found that one element has usually replaced 
another element in one of the compounds present. 

Further, a certain mass of one element is found to displace con- 
sistently the same quantity of the other element. ‘These two quan- 
tities are said to be equivalent. 

It is convenient in practice to adopt some one element to which 
all the others refer, and thus the equivalent of an element is defined as 
the number of parts (or grams) of an element which are replaceable 
by, or combine with, or are chemically equal to, one part (or gram) 
of hydrogen. 


EXERCISES IN DETERMINATION OF EQUIVALENTS 


As in a great many of these determinations a volume of hydrogen 
will be collected, which must be converted into a mass, the first exer- 


90 TEXTILE CHEMISTRY 


cise is to determine the relationship which exists between these two 
quantities. 

1. To determine the Mass of 1 Intre of Hydrogen. 

Use the special apparatus, diagrams of which are shown in Figs. 
140 and 141. 

Carefully weigh the light apparatus (Fig. 140) when fitted up with 
a small piece of magnesium rod in the T.T., covered with water, and 
strong sulphuric acid partly filling the drying bulb. 

Attach it to the collecting apparatus A to A’; arrange the level of 
water in aspirator and gauge tube to be the same by drawing off water 
at B. 


To Flask 


Gently warm the T.T. Air is expelled through acid. Cool. 
Acid is drawn into outer tube, and hydrogen is liberated, passes 
through the drying bulb and into the aspirator, causing the water in 
gauge tube gradually to rise. Draw off water at B into a 250 c.c. flask 
at such a rate as will keep the surfaces of the water level. 

When all action is over 

(1) Read thermometer in aspirator (say #¢° C.). 

(2) Read atmospheric pressure on barometer (say P mm.). 

(3) Detach the light apparatus and carefully weigh to find the 
loss in mass, which gives the mass of hydrogen evolved (say=m grams). 


THE ELEMENTS OF CHEMICAL THEORY 91 


(4) Carefully find the volume of water collected by filling up the 
250 c.c. flask from a burette—which gives the volume of hydrogen 
evolved (say = a@c.¢.). 

Volume corrected to N. ee P. (i.e. 0° C. and 760 mm. pressure) 

a 
yee (00367 x a * 


This has a mass of m grams. 
m 


*, 1 litre weighs ep | 


T+ (00367 xt ~ 760 
Correct value = -0899 gram. 
2. To determine the Equivalent of a Metal by dissolving in Acid 
and collecting the evolved Hydrogen. 


map LbY Boyle’s and Charles’s law]. 


Ditute Acid 
SL (in glass vessAl ) 
Pane 


Magnesium Fi¢442 


Several variations of apparatus are given according to the metal 
to be used. 

(a) Magnesium. Weigh out very accurately about -1 gram of 
freshly cleaned magnesium ribbon. Put it into the bottom of a 
narrow T.T., and fill with water by dropping into a small glass or 
enamelled-iron pneumatic trough. 

Fill the larger tube—half with dilute sulphuric acid and half with 
water—close with thumb, place in trough, slip in the T.T. (Fig. 142) 
and raise to vertical position. 

When the magnesium is all dissolved, take the temperature of the 
water and transfer the tube carefully to a tall cylinder of water to 
bring to atmospheric pressure, which is equal to the barometric 
pressure (Fig. 143). 

Mark the level with a strip of paper, and find the volume of the 
gas by pouring in water from a measuring vessel. 

Correct this volume to 0° C. and 760 mm. pressure, and convert 
into a mass (in grams) by means of the value found in Exercise 1. 

By “ Rule of Three,” find 

How many grams of magnesium would be required in order to 
liberate 1 gram of hydrogen (i.e. the equivalent of magnesium). 


92 TEXTILE CHEMISTRY 


The apparatus shown in Figs. 144 and 145 can also be used. 

(b) Zinc, Iron, Aluminium. Use the apparatus shown in Fig. 144. 

Carefully weigh a small piece of metal and place in T.T. Fill it 
with water, and close the tap. 

Place dilute acid in the funnel, fill the collecting tube, invert i 
into the funnel, and open the tap. 


The acid flows down and ultimately acts upon the metal—the 
gas evolved being collected in the closed tube. 

The temperature of the gas must be determined in each case, and 
the volume corrected to atmospheric pressure as shown in Fig. 143. 

Correct the volume and find its mass as in (a) above. : 

For zinc and iron, use either dil. sulphuric or dil. hydrochloric 
acid. 


La 
< 
es 


os 
* 
o] 
aed 


THE ELEMENTS OF CHEMICAL THEORY 93 


For aluminium use either caustic soda solution or hydrochloric 
acid (1 volume water, 1 volume strong acid). 

It is desirable, and in some cases necessary, to warm gently. 

Apparatus shown in Fig. 145 is to be used with aluminium and 
caustic soda. 

Be careful that the stoppers fit very tightly and are of rubber. 

Calculate how many grams of the given metal are required to 
liberate 1 gram of hydrogen. 

3. To determine the Equivalent of a Metal by Precipitation with 
another whose Equivalent has been already determined. 

(a2) Prepare a solution in water of a soluble salt of the metal 
whose equivalent is to be determined, e.g. 

For copper, use copper sulphate. 

»  sdlver, ,, silver nitrate. 
5 . -t8n, ,, stannous chloride in hydrochloric acid. 
» lead,  ,, lead acetate. 

(0) Carefully weigh a quantity of the precipitating metal, which 
must be as pure as possible. 

Zine (foil) will precipitate copper, silver, tin, lead. 

Copper (foil) will precipitate silver (in hot solution). 

Magnesium will precipitate silver, iron, cobalt, zinc, nickel, 
gold, platinum, bismuth, tin, mercury, copper, lead, cadmium. 

Iron will precipitate copper. 

Add the precipitating metal to the solution contained in a small 
beaker, stir from time to time with a glass rod, until all the precipi- 
tating metal is dissolved. 

Collect every particle of the precipitated metal, either on a filter 
paper (of known mass) or in a small crucible ; wash well first with hot 
distilled water, then with alcohol; and dry in a steam oven. When 
completely dry, weigh. 

Finally, calculate the equivalent of one metal in terms of the 
other ; and then, to obtain the equivalent in reference to hydrogen, 
multiply this result by the equivalent of the known metal. 

4. To determine the Equivalent of an Element by preparing a Com- 
' pound of the Element with another whose Equivalent has been previously 
determined. 

(a) Oxygen. (i) Prepare tin oxide. Use a known mass .of 
granulated tin. 

Place it ina crucible and add strong nitric acid from a pipette drop 
by drop (Fig. 146). When all the tin is oxidized, ignite and weigh. 

(1) Calculate what mass of oxygen has combined with the equi- 
valent weight of tin. 

(2) Prepare magnesium oxide by the action of dilute nitric acid 
on a known mass of the metal, and perform similar calculations. 


94. TEXTILE CHEMISTRY 


(0) Silver. Prepare pure silver oxide by allowing baryta water 
to filter into a small flask of silver nitrate solution. Cork at once and 
shake ; allow the oxide to settle ; decant liquid; wash several times 
with hot water, and dry in steam oven. Put two or three grams into 
a hard glass tube of known mass. Attach to an aspirator, heat, and 
collect the evolved oxygen. Find its mass—check by weighing the 
residue in the tube. 

Calculate the amount of silver which combines with eight grams 


of oxygen. 
Table of Approximate Equivalents 


Hydrogen = 1 Sodium = 23 
Carbon =) 00 Tron =i 20 
Nitrogen = 4-7 Copper. o=982 
Oxygen om 8 Zinc = O27 
Aluminium = 9 Chlorine = 35:5 
Magnesium = 12-2 an = 59 
Sulphur = 16 Silver = 108 


Equivalence is an experimental fact and shows no variation— 
except that certain elements (that form two series of salts) give one 
or other of two values, depending upon which class of‘ compound is 
being experimented with, e.g. 

Mercury 100 or 200. Copper 32 ior :~(64. 
Tin 59 or 118. Iron 18-67 or 28. 
These values are related to each other as 1: 2, 2: 3, etc. 


THE THEORY OF VALENCY 
is an attempt to explain, chiefly from logical considerations, the 
phenomenon of equivalency. It is found that if the atomic or com- 
bining weight of an element be divided by its equivalent, in every 
instance the quotient is a whole number (1, 2, 3,4,5). These numbers 
are assumed to measure the ratio of chemical combining powers of the 
respective elements. 


Table of Valencies or Atomicities 


Monads, . Diads. Triads. Tetrads. Pentads, 
Chlorine Calcium Aluminium Carbon Nitrogen 
Hydrogen Copper Nitrogen Tin Phosphorus 
Potassium Iron Phosphorus 
Silver Zinc 
Sodium Lead 

Magnesium 
Oxygen 
Sulphur 


Tin 


ea, Oo oe a ae eee Ene re eS a ae 


MB -aty 
» Sia art 


A SARL ORB EE 


a4 
~~ 


Lou 


THE ELEMENTS OF CHEMICAL THEORY 95 


Those giving a quotient of 1 are termed monads or monovalent 
elements. 
Those giving a quotient of 2 are termed diads or divalent elements. 
Those giving a quotient of 3 are termed triads or trivalent elements. 
The relationship existing among atomic weight, equivalence, and 
valency may be summarized as :— 


At. Wt. 
V 


and as in most cases At. Wt. = Molecular Wt. ~ 2 and Molecular Wt. 
= Vapour Density x 2, 
Therefore 


Atomic weight — Valency = Equivalent or EK = 


v.d. 
V a 


Thus if the vapour density of an element = 16 and its equivalent 


is 8, its valency is ae 2 (i.e. it is divalent). 


GRAPHIC REPRESENTATION OF VALENCY 


Ammonia Gas H—N—H Mercuric Oxide Hg=O 
| Carbon Dioxide O=C=O 


H Caustic Soda Na—O—H. 


Hydrogen Chloride H—Cl Cl 


Water H—O—H 


H—O O 
Seiphisin: Avid \sJ 


H—o” No 
Copper Oxide Cu=O 
Potassium Chlorate 


panes 
K—0—OK 


Aluminium Chloride AlCl 
Cl 


LA 
Magnesium Chloride MeN 


ve 
Chloroform H—C<—Cl 
Na 


Calcium Hydroxide 


\ 
Nitric Acid YN—O—H 
oF H—O—Ca—OH 


SYMBOLS, FORMULZ AND EQUATIONS 


Symbols were devised by Dalton to represent one atom of the 
respective elements. He used circles, e.g. O, ©, O, ®, for certain 
of the non-metallic elements, and circles containing letters for the 
metals. . Berzelius brought symbolic representation to its present 
form by omitting the circles and using initial letters throughout, e.g. :— 


96 


Aluminium . 
Chlorine 
Iron (Ferrum) 


Mercury (Hvdrareyrdin) Hg 


Silver (Argentum) 
Phosphorus . 
Barium . 


Copper (Cuprum) 


Lead (Plumbum) 


Sodium (Natrium). 


Calcium . 


The symbol denotes :— 
1. One atom of the element. 


2. The number of parts by weight given as its atomic or combining 


weight. 


It is not to be used as an abbreviation for the name nor as chemical 


shorthand. 


Combinations of symbols are termed Formule. They (usually) 
represent the proportions by weight and the number of atoms in which 


TEXTILE CHEMISTRY 


Hydrogen 
Magnesium . 
Oxygen . 


Potassium (Kalium) 


Carbon 

Iodine 

Nitrogen 

Sulphur 

Zinc ar 
etc. 


the elements exist in one molecule of the compound. 


If a multiple of the atomic weight is denoted, this multiple is 
written as an index figure to the symbol at the botiom, e.g. H., O3, Pa, 
Cl,. A bracket has the same significance as in arithmetic, e.g. (COOH). 


means twice all the symbolic value in the bracket. 


A figure in front of an expression has the same value as before a 
bracket, and carries its influence to the end of the expression. 


7H,O means seven times the sum of H, and O. 


The formula of a substance represents one molecule of that q 


substance. 


Formulz of some Common Compounds 


Hydrochloric Acid . 
Sodium Chloride 
Calcium Chloride 
Potassium Chloride. 
Ammonium Chloride 
Ferric Chloride . 
Silver Chloride . 
Lead Chloride 
Magnesium Chloride 
Zine Chloride 

Nitric Acid . 

Silver Nitrate 
Sodium Nitrate 
Potassium Nitrate . 
Copper Nitrate . 
Sulphuric Acid . . 


. HCl 

. NaCl 

. CaCl, 

ee <0) 

. NH,Cl 
. Fe,Cl, 


Copper Sulphate 
Ferrous Sulphate 
Magnesium Sulphate 
Zinc Sulphate 
Barium Sulphate 
Calcium Sulphate 


Ammonium Sulphate . 


Sodium Sulphate 
Potassium Sulphate 
Carbon Dioxide 
Calcium Carbonate 
Sodium Carbonate . 
Sodium Bicarbonate 
Calcium Bicarb. 


Ammonium Carbanated 


Potassium Chlorate. 


. FeSO,.7H,0 
. MgSO,.7H,0 — 
. ZnSO,.7H,0 — 
: BaSO, 
. CaSO, 


. KCIO; 


eg! eS) ee 


Pama 


SZ Honor 


git a pe 


CuSO,.5H,0 — 


(NH,).SO,4 


CaH 2(CO 3) 2 
(NH,),CO; 


THE ELEMENTS OF CHEMICAL THEORY 97 


Potassium ee Mercuric Oxide. . . HgO 

BIG. ys K.Mn,Og WARS (SIG ce Sd iat AUD 
Puormiamy  . . . CHC, Ozone . ot Gala 
Water . . 7 sO Sodium Hydrate . . NaOH 
Carbon Monoxide Jet yy & 8) Calcium Hydrate . . Ca(OH), 
Sulphur Dioxide. SO, Barium Hydrate . . Ba(OH), 
Silicon Dioxide (sand) . SiO, Copper Hydrate . . Cu(OH), 
Manganese Dioxide. . MnO, Potassium Hydrate. . KOH 
Magnesium Oxide . . MgO Hydrogen Sulphide. . H,S 
Sulphur Trioxide . . SO; Carbon Disulphide. . CS, 
Copper Oxide . . . CuO Ferrous Sulphide . . FeS 
Nitrous Oxide . . . N,O Ammonia . i NH, 
Nitric Oxide. . . . NO Ammonium Hydrate . NH,OH 
Barium Peroxide . . BaO, Mercuric Iodide. fee: 
Litharge ee 2 2 EDO AUT Al,(SO,)s- K,80,.24H,O 
hed ueed  . .... «.Pb,0, Bleaching Powder . . Ca(OCl)Cl 
Lead Peroxide . . . PbO, Oxalic Acid. . . . (COOH), 
Ferric Oxide . . . Fe,O;3 (Ethyl) Alcohol a este. OH 
Calcium Oxide . . . CaO 


AN EQUATION 

represents quantitatively a chemical change or reaction. 

+ on the left means ‘“ chemically reacting with.” 

+ on the right means “ and.” 

= or > means “ produces, forms, yields,” etc. 

An equation always contains at least two formule. The only 
points of equality are: 

(1) That the sum of the combining weights on one side must equal 
the sum of the combining weights on the other. 

(2) The number of atoms of each element must be the same on 
each side. 

To solve an arithmetical example an equation should be used in 
the following manner : : 

Step 1. Select the correct equation. 
Enter the respective combining weights. 
3. Total them up for each formula. 
4. Underline the terms required. 
5. Get the statement for “rule of three.” 


99 


EXAMPLE 
““How much copper would be required to produce 8 grams of 
copper nitrate by the action of nitric acid on the metal ? ” 
Step 1. 3Cu + 8HNO, = 3Cu(NO;), +4H,0 + 2NO 


Pe See G4 1 14 14 
14 tie) cok ute 
48 Parad aryl 1G 30 x 2 
63 x 8 64 18 x 4 
188 x 3 
eo. 102 504 564. 72 60 
A ~ 


98 TEXTILE CHEMISTRY 
Step 5. 564 grams of copper nitr. are obtd. from 192 grams of copper, 


A 192 
therefore 1 gram or 5 ate T= oe ” Faq ei 
3 192 x 8 
99 grams 399 99 are 99 eer. 7,F Ge: 9 9 
== 2-72 grams. 
Equations representing some well-known Chemical Reactions 
Hg +1 = Hgl. 
Mercury and iodine combining to form mercuric iodide. 
Fe +S = FeS. 


Iron and sulphur combining to form ferrous sulphide. 
FeS + H,SO, = FeSO, + HS. 
Ferrous sulphide and dil. sulphuric acid reacting to produce ferrous 
sulphate and sulphuretted hydrogen gas. 
2Na + 2H,O = 2NaOH + H,. 
Sodium acting on water to produce sodium hydrate (caustic soda) 
with the liberation of hydrogen gas. 
3Fe + 4H.0 = Fe,0, + 4H. 
-Iron heated in a current of steam—black oxide of iron formed and 
hydrogen liberated. 
Zn + H,SO, = ZnSO, + Hg. 


Zine and dil. sulphuric acid react to produce zinc sulphate and 


hydrogen. 
2KCI1O; = 2KCl + 30,. 
Potassium chlorate is decomposed by heat into oxygen and potassium 
chloride. 
SO, + O = SO,. 
Sulphur dioxide and oxygen passed over heated platinized asbestos 
unite to form sulphur trioxide. 
CuO + H, = Cu + H,0. 
Copper oxide heated in a current of hydrogen is reduced to metallic 
copper, with formation of water. 
CaO + CO, = CaCOQOs. 
Calcium oxide (lime) exposed to carbon dioxide combines to form 
chalk. 

The following equations represent chemical changes that have 
taken place while performing some simple experiments in the labora- 
tory. Write in words the meaning of each in a similar manner to that 
shown above. 

1. Mg + O = MgO 5. Zn + 2HCl = ZnCl, + Hy 
. Fe + H,SO, = FeSO, + H, 
. CuSO, + Fe = FeSQ, + Cu 


. 2HgO = 2Hg + O, 
. HCl+ NH, = NH,Cl 


bo 
= 
=} 
= 
+ 
aN 
an 
© 
oS 


= MnCl, + 2H,O+ Cl, 
3. CuO + H,SO, = CuSO, + H,O 
4. Cc + O, = CO, 


ole ot | 


THE ELEMENTS OF CHEMICAL THEORY 99 


10. CaCOs + 2HCl 19. Zn + CuSO, = ZnSO, + Cu 
11. HCl + NaOH = NaCl + H,O 21) BP, + 60, = 2P.0, 
12. Na,CO, + 2HCl 22, 2Ke, -+ 30, = 2Fe,0, 
= 2NaCi + H,O + CO, 23. He + O = HgO 
18. SO, +0 + H,0 = H,SO, 24, KOH + HNO, = KNO, + H,O 
14. 2H,0 = 2H, + O 25. CaCl, + 2AgNO, 
15. 3Fe + 4H,O = Fo,0, + 4H, = 2AgCl + Ca(NO,), 
16. Mg + H,SO, = MgSO, + H, 26. NH,Cl + NaOH 
17. CO+0 =CO, = NH, + NaCl+ H,O 


18. Na,S + 2HCl = H,S + 2NaCl 
EXERCISES IN CHEMICAL ARITHMETIC 


1. How much oxygen can be obtained by igniting 20 grams of 
potassium chlorate ? 

2. For how long must steam be passed over red-hot iron at the rate 
of 2 grams per minute, in order to produce 8 grams of hydrogen ? 

3. How much ammonium chloride is required in order to prepare 
10 grams of ammonia from a mixture of ammonium chloride and lime ? 

4. How much chlorine could be obtained by acting on 5-6 grams of 
manganese dioxide with excess of hydrochloric acid and warming the 
mixture ? 

5. How much rock salt would it be necessary to use in order to 
prepare a 20 per cent. solution of hydrochloric acid in water, using 100 
grams of water ? 

6. How much water can you obtain by reducing 25 grams of copper 
oxide with hydrogen ? 

7. How much carbon is required to reduce 165 grams of carbon 
dioxide to carbon monoxide ? 

8. How much sulphur is there in 268-3 grams of crystallized zine 
sulphate ? 

9. How much zinc is required to precipitate 100 grams of lead from 
a solution of its nitrate ? 

10. How many lb. of nitrogen are contained in 1 ton of ammonium 
sulphate and sodium nitrate respectively ? 

11. How much carbon is there in 1 kilogram of cane sugar ? 


RELATIONSHIP BETWEEN THE VOLUME AND MASS OF 
‘GASEOUS ELEMENTS AND COMPOUNDS 


If equal volumes of different gases (under the same conditions of 
temperature and pressure) be accurately and carefully weighed, it is 
found that their weights vary (Section VI, page 47). The lightest is 
hydrogen, 1 litre of which at N.T.P. weighs 0-0899 gram—some- 
times called 1 crith. Oxygen weighs 16 times as much, ammonia 8-5 
times, hydrogen chloride 18-25 times, etc. 

This relative density of a gas in relation to hydrogen is called its 
Vapour Density. (See Table, page 47.) 

Now, Avogadro’s Law states that these litres all contain the same 


100 TEXTILE CHEMISTRY 


number of molecules. ‘Therefore the same ratio (i.e. v.d.) gives the 
relative weights of the respective molecules of gas. 

Then, as we have thus obtained the weight of each molecule of gas 
in terms of the weight of one molecule of hydrogen, the question comes, 
‘* What is the weight of 1 molecule of hydrogen in terms of our unit, 
i.e. the weight of 1 atom of hydrogen ?’’ Careful chemical research 
has answered this as “two.’”? Therefore the molecular weights of gases 
are obtained by multiplying the v.d. by 2. 

Now, if 1 litre of hydrogen at N.T.P. weighs -0899 gram, then 
22-4 litres of hydrogen will weigh 2:02 grams, i.e. twice the atomic 
weight (1-01) of hydrogen. 

Thus 22-4 litres of any elementary or compound gas at N.T.P. will 
weigh its molecular weight in grams. 


EXERCISES 


1. Find the volume of hydrogen (at N.T.P.) which would be 
evolved by treating 10 grams of zinc with hydrochloric acid. 

2. What volume of oxygen at N.T.P. would be produced by strongly 
heating 5 grams of potassium chlorate ? 

3. What weight of common salt would be required to furnish 
sufficient hydrogen chloride to neutralize 100 grams of a 30 per cent. 
solution of caustic soda ? What would be the volume of the gas at 
NTP. t 


narra ee ae es ee 


coh ark 


SECTION X 
CARBON AND SOME OF ITS COMPOUNDS 


tary condition it occurs as diamond and graphite. Combined 

with other elements like hydrogen, oxygen, and nitrogen, it 
forms thousands of compounds which are essential to life and vital 
processes generally. 

From many of these compounds carbon can be prepared in an 
amorphous condition, e.g. charcoal, lampblack, gas carbon, etc. The 
phenomenon of an element occurring in different physical conditions is 
termed allotropy, and the varieties are known as allotropic modifica- 
tions. 

Diamonds are octahedral crystals of high sp. gr. (3-5), are ex- 
tremely hard, and highly refractive to light. These two properties 
are mainly responsible for the two chief uses, i.e. for rock boring and 
cutting, and use as a gem. 

Lavoisier showed by burning a diamond in oxygen—when carbon 
dioxide was produced—that it contained carbon, and later Davy 
showed that it was pure carbon. 

Graphite, also known as black-lead or plumbago, is a greyish 
black solid with a distinct lustre, and occurs very widely distributed 
throughout the world, i.e. Iceland, Siberia, Ceylon, Canada, etc. It is 
now produced in large quantities artificially at Niagara by the Acheson 
process. It is used as (1) a lubricant, (2) a polishing medium for 
shot, ironwork, gunpowder, etc., (3) an ingredient in the “lead” of 
pencils, (4) a film for electrotyping, (5) an ingredient in plumbago 
crucibles. 

It is soft and soapy in texture, and is attacked when warmed with 
a mixture of potassium chlorate and nitric acid. 

Amorphous carbon occurs in many forms, e.g. charcoal, gas, 
carbon, lampblack, and may be prepared from almost any organic 
tissue or substance—wood, starch, cheese, sugar, coal, turpentine, etc. 

The older style of charcoal production was to make heaps of wood, 
cover with sods, and set the mass on fire. This was extremely waste- 
ful, and when wood is carbonized to-day it is destructively distilled 
in ovens in a similar way to that adopted for coal, the result being that 


101 


Ors: is the most wonderful of all elements. Inthe elemen- 


102 TEXTILE CHEMISTRY 


many valuable by-products are obtained of which pyroligneous acid 
(used as a source of acetic acid), methyl alcohol, and acetone are the 
most important. 

The destructive distillation of wood can be illustrated on a small 
scale by using the apparatus shown in Fig. 147. The test tube con- 
tains sawdust. In bottle A some of the most easily condensed pro- 
ducts are obtained. Bottle B, containing water, serves to wash the 
gas free from others, and an inflammable gas passes along, which may 
be ignited at C. 

Lampblack is prepared by burning oil in a small supply of air. 
A very smoky flame is produced, due to the presence of finely divided 
carbon. This soot is collected on blankets hung in chambers through 
which the smoke is made to pass, a process similar to the collection in 
chimneys. Lampblack is used for printer’s ink and black paints. It 
will not bleach. 


F1G.148 


Charcoal of a much purer quality than that obtained by the 
destructive distillation of wood is prepared by adding strong sulphuric 
acid to a concentrated solution of sugar in water. The black mass 
produced is washed free from acid and dried. 

Coke and gas carbon are obtained in the destructive distillation 
of coal. The former contains about 90 per cent. of carbon, Aes latter 
nearly 100 per cent. 

Animal charcoal is prepared by roasting bones. Its average 
composition is 10 per cent. carbon, 88 per cent. calcium phosphate, and 
2 per cent. other substances. 

It has a very considerable application in industry as a deodorizer 
and decolorizer, but it requires frequent re-ignition if its efficiency is 
to remain unimpaired. 

Coal, to the large deposits of which in this country England 
largely owes her commercial supremacy, is a very impure form of 


COMPOUNDS OF CARBON 103 


carbon, and includes compounds of carbon with hydrogen, nitrogen, 
etc. It is a mixture evidently formed from a geological deposit of 
ancient luxurious tropical vegetation. 

It is the chief British fuel, and the source of one of the chief means 
of artificial illumination. For the latter purpose it is destructively 
distilled to produce “coal gas.”’ Fig. 148 shows the principle of the 
method. 

R represents the retort containing the coal, H the hydraulic main, 
T the tar-pit, C the coolers, S the scrubber for removing by solution the 
ammonia produced, P the purifier (containing iron oxide or lime), and 
G the gasometer. 

Coal tar, which consists of a mixture of a very large number of 
compounds of carbon, is also destructively distilled, and the products, 
as they are evolved at different temperatures, are collected in several 
fractions. ‘The residuum is known as pitch. 

From these fractions chemicals are obtained which severally serve 
as the starting-points in the manufacture of a series of ‘‘ intermediate 
products,” these in their turn being used for the preparation of :— 

(a) Coal-tar dyes; (6) flavouring, sweetening, and colouring 
materials; (c) drugs and disinfectants; (d) perfumes; (e) explo- 
sives ; (f) organic solvents. 

The chief compounds of carbon include those with :— 

1. Oxygen. The Ox1pEs.—Carbon monoxide, carbon dioxide. 

2. Hydrogen. The HypRocaRBons.—Marsh gas, acetylene, ethyl- 
ene, benzene, toluene, naphthalene, anthracene. 

3. Oxygen and hydrogen. The CaRBoHYDRATES (starches, 
sugars), ALCOHOLS, ALDEHYDES, ErHeErs, AcIDs. 

4, A metal and oxygen. The CarBonaTEs, such as chalk, marble, 
aragonite, witherite, ironstone, soda ash, magnesite, etc. 

A few of these compounds will now be considered in detail. 

Carbon dioxide. A heavy, colourless gas is found to be produced 
as a result of combustion, respiration, and fermentation, which has 
been known at various times under various names, e.g. gas sylvestre, 
choke-damp or after-damp, fixed air, chalk gas, carbonic acid gas, 
carbonic anhydride, but which is usually termed carbon dioxide. 

It is present in fresh air, mixed fairly uniformly, to the extent of 
0-03 per cent. to 0:04 per cent. by volume, and is found in certain 
natural mineral waters, e.g. Apollinaris, Johannis, Perrier, Apenta. 
It also exudes from vents and fissures in volcanic regions. 

Its presence in air is due almost entirely to respiration and com- 
bustion. From it it is assimilated by plants and vegetation generally, 
being converted in the “leaf laboratories’ into starch and sugar. 

The earth crust contains many carbonates, which are metallic 
oxides in combination with the gas, 


104 TEXTILE CHEMISTRY 
T'o prepare the Gas :— 


1. Act on a carbonate with acid, e.g. marble and dilute hydro- 
chloric, magnesite and dilute nitric, sodium carbonate and sulphuric 


(Figs. 149, 150). 
2. Heat charcoal in a good supply of air or oxygen (Fig. 151). 
3. Ignite certain carbonates, e.g. chalk, magnesite. 


4. Ferment sugar with yeast (Fig. 152), keeping the temperature 
about 30° C. Enormous quantities of carbon dioxide are obtained 


F1G L5L 


in this way from breweries and distilleries, condensed into bottles, 
and used in the manufacture of mineral waters. 


PROPERTIES 
It is a heavy colourless gas (14 times as heavy as air). Many 
experiments may be performed to illustrate this property, e.g. a beaker 
full of it may be weighed and compared with the weight of the same 
beaker when full of air ; it may be poured from one gas jar to another 
like a liquid ; a soap bubble that would fall in air may be floated in a 
bell jar of the gas (Fig. 153). 


ad 


eee g Oe Te 


CARBON DIOXIDE | 105 


The soap bubble is best blown by using a piece of glass tubing about 
4 inch diameter, which contains a plug of cork in which “ gutters ” 
have been cut. 

It will not support ordinary combustion, e.g. a taper, a candle 
flame, and even that from burning turpentine will be extinguished by 
it ; but it will support the combustion of burning magnesium, with the 
liberation of carbon and the formation of magnesium oxide (black and 
white residue). | 

It is very soluble in caustic soda, forming sodium carbonate. It 
is soluble in water, especially under pressure. Soda-water, beer, 
lemonade, champagne contain it, and thereby “ sparkle ” when opened. 


FiG.153 


It is easily liquefied. ‘“Sparklets ” contain liquid carbon dioxide. 
It has a feeble taste, slightly acid reaction when dissolved in water, and 
a pleasant smell. 


Uses. 1. For making mineral waters. 

2. For extinguishing fires—hand grenades. 

3. As a refrigerating agent—liquid carbon dioxide plants are very 
efficient. 

4. For aeration of bread and pastry—baking powder liberates it. 

5. As an asphyxiating agent—the lethal chamber at the famous 
Lost Dogs’ Home in Battersea is worked with it. 

6. For medicine—Seidlitz powders, health salts, fruit salts, when 
mixed with water, liberate it. 

7. As an indicator of impurities in an atmosphere—e.g. in mills 
and schools. 

8. As food for plants. 


106 TEXTILE CHEMISTRY 


PRACTICAL EXERCISES 


1. Test for Carbonates. Use specimens of each of the following 
carbonates : Calcium carbonate, sodium carbonate, barium carbonate, 
ammonium carbonate. Test the action of dilute acid on each. Note 
if carbon dioxide is evolved. Use the apparatus shown in Fig. 154. 

Then determine which of the following substances are carbonates 
or contain carbonates: Iceland spar, egg shell, washing soda, mag- 
nesite, oyster shell, oxalic acid, cryolite, baking powder, old mortar. 

2. To distinguish Chalk from Quicklime :— 

(a) Add water, and note result—solubility, temperature. 

(b) Try effect of heat on each, and note if any alteration occurs in 
weight. 

(c) Try effect of dilute hydrochloric acid on each. 

3. Experiment with the by-product from the manufacture of carbon 
dioxide from marble and hydrochloric acid, which is calcium chloride. 

Evaporate the liquid to dryness, abstract the solid calcium chloride, 
and describe its colour, texture, action on exposure to air. 


Ae 


4. T’o determine the Mass of Carbon Dioxide evolved by the action 
of an AcID on a given mass of a carbonate :— 

This is done, as a rule, by “ difference,” i.e. the carbon dioxide is 
expelled into the air, and the residue is weighed ; which is very simple 
in principle, e.g. perform the following experiments :— 

(a) Half fill a small flask (2 oz. capacity) with dilute /hydrochieas 
acid, and accurately weigh it (= a@ grams). 

(b) Accurately weigh a small lump of marble (= 6 grams). 


(c) Drop the marble into the flask and allow the acid to dissolve it 


completely. Carbon dioxide is expelled. 
(d) When action has ceased, weigh again (= c grams). 
Then 6 grams = mass of carbonate taken, 
and a + b —c = mass of carbon dioxide evolved. 

100(a + b — c) 


Percentage of carbon dioxide in marble = 5 


= 
de, 4 
x, 


CARBON DIOXIDE 107 


Compare the result obtained with the correct percentage (44 per 
cent.). The error is due to the following causes :— 

(a) Some of the carbon dioxide is left dissolved in the liquid. This 
tends to decrease the percentage. 

(6) Water is evolved with the gas. This tends to increase the 
result. 

(c) Carbon dioxide fills the flask in place of air. This decreases the 
percentage. 

The first error can be corrected by just boiling the liquid over a 
small naked flame after all action in the cold has ceased ; the third by 
sucking out the carbon dioxide; the second necessitates a special 
device for drying the gas as it passes out. 

Fig. 155 shows a simple method, using cotton wool; the gas is 
sucked out with a glass tube, not shown in the figure. In Fig. 156 a 
drying-tube filled with pieces of fused calcium chloride, or pumice 
moistened with strong sulphuric acid, is used. The carbonate is 
weighed into the flask; the small test tube contains strong hydro 
chloric acid. 


F1G.158 F1G.160 


Fig. 157 is merely a modification of Fig. 156. Dzlute acid is put 
into the tube ; the carbonate is weighed into the small test tube, which 
contains a small hole in the bottom. 

Fig. 158 is similar in principle. The strong hydrochloric acid is con- 
tained in the pipette, and the entran-e of it is regulated by a small clip. 

Figs. 159 and 160 show other forms of drying apparatus in which a 
few drops of strong sulphuric acid are used in place of the moistened 
pumice. 

Fig. 161 is Schrotter’s, one of the standard pieces of apparatus for 
this determination. The carbonate is put in by removing the stopper. 
The pipette contains the acid to decompose it, and the drying 
arrangement contains strong sulphuric acid. 


108 TEXTILE CHEMISTRY 


Fig. 162 is a very efficient apparatus designed by the author some 
years ago and made by Messrs. F. E. Becker & Co., of Hatton Wall, 
London. 

To use the apparatus, remove the rubber stopper carrying the 
pipette and drying bulbG. Weigh the test tube, both before and after 
putting in the carbonate (difference in mass= weight of carbonate used). 
Into the small test tube C put a few drops of strong sulphuric acid. 
Remove stopper, and by suction, fill the pipette A with acid, say 
hydrochloric, pinch the rubber tube B, and replace. Put into E a 
little water, replace the stopper and hang the whole to the specific- 
gravity hook of a balance and weigh. 


Ue A 


Slightly squeeze the rubber tube B between the finger and thumb, 
as in diagram, and allow a few drops of acid to drop from A. The 
liberated gas escapes through the drying apparatus G. When the 
action is over, remove the stopper, and attach B to a suitable ap- 
paratus, and aspirate until the carbon dioxide in E is eliminated. 
Replace stopper and weigh the whole apparatus—the loss of weight 
represents the evolved carbon dioxide. 

If still greater accuracy is desired, it is well to arrange this ap- 
paratus in combination with tubes and aspirator as shown in Fig. 163. 

A is the decomposition apparatus used as described above. 


CARBON DIOXIDE 109 


It is connected at 1 with B, which will absorb the carbon dioxide 
evolved from A. 

The gain in weight of B should equal the loss in A. 

C is an aspirator by means of which a current of air can be drawn 
through A in order to expel every trace of carbon dioxide from it. 

To do this, after the decomposition of the carbonate is complete, the 
top of the acid pipette is connected at 2 with the tube D, through which 
the air has to pass before it reaches A. D contains caustic soda and 
sulphuric acid to ensure that when it enters A it contains no moisture 
and carbon dioxide. 

5. T'o determine the Mass of Carbon Dioxide evolved by the action 
of heat on a carbonate :— 

Not all carbonates are decomposed by the action of heat. Use for 
this exercise precipitated chalk or magnesite. 


NN 


Thoroughly dry a porcelain crucible by heating it for five minutes 
over the bunsen flame, cool, and weigh it very accurately. Put in 
sufficient of the carbonate to form a layer about one-eighth of an inch 
thick on the bottom of the crucible, and reweigh to find the amount 
used. 

Heat strongly over the bunsen flame or put in a muffle furnace for 
one hour, with the lid of the crucible removed. 

Cool in a desiccator and weigh again. Find and record the loss 
that has occurred. Reheat in a similar manner for ten or fifteen © 
minutes, cool and reweigh. Find and record the second loss. If it 
exceeds 0-001 grams, repeat the heating until no greater loss is obtained, 
when it may be assumed that the carbonate is completely decomposed. 


110 TEXTILE CHEMISTRY 


Find the total loss and calculate to a percentage. The weighings 
should be recorded as follows :— 
Mass of crucible ++ Carbonate 


9 9 only wee ” 
Then amount of carbonate used = gm 
Crucible + Carbonate before heating a 3 

29 ah re) after ” — 2” 

First loss = ‘gm 
Crucible + Carbonate after first heating a wy 

ee) as 2? re) second » =. 29 

Second loss a gm 


and so on. 


6. Black’s Researches on Chalk, or to compare quantitatively the 
composition (with respect to the proportions of the two oxides they 
contain) of marble, Iceland spar, egg shell, precipitated chalk, oyster 
shell, etc. 

(a) Determine the percentage of calcium oxide present in each of 
the following substances—express as CaO = x per cent. 

(6) Determine the percentage of carbon dioxide present in the 
same substances—express as CO, = y per cent. | 

1. By action of heat alone. 2. By action of acid. Substances to ~ 
be used: Precipitated chalk, marble, Iceland spar, egg shell (cleaned 
and dried), oyster shell, calcite, calc spar. 

Methods to be followed are those just described. Take care to 
powder the substance thoroughly if it is not in that condition, and use 
small quantities for the experiments. 

Collect and tabulate the results :— 


Composition. 


Substance 
used. 


Pereentage Percentage Percentage 
CaQ. COz. Total. 


Chalk. 


Marble 


CARBON DIOXIDE 111 


From an inspection of the series of results, what deductions do 
you make ? 

7. To determine the Volume of Carbon Dioxide evolved by the action 
of an acid on a carbonate. 

Fit up the apparatus as shown in Fig. 164. Test to see if it is 
perfectly air-tight ; until it is so, it is useless to proceed. 

Weigh out into the flask (preferably by use of a weighing-bottle) a 
few grams of the carbonate. Cover it with about 10 c.c. of water. 
Fill the pipette with strong hydrochloric acid, and refit the flask. 
Liberate the acid a few drops at a time until the carbonate has com- 
pletely dissolved ; then warm the liquid to expel the dissolved gas. 
Allow the gas to cool down to the temperature of the laboratory, 


FIG. 164 


taking care to keep the end of the delivery tube from the aspirator 
under the surface of water in, or from, the collecting vessel. 

Measure the volume of water collected, deduct the volume of acid 
run into the flask, and if an accurate result be required, correct this 
volume to N.T.P. Calculate the volume of gas obtainable from 1 gram 
of the carbonate. 

Why is the “ Winchester ” used ? Would it be necessary (say) in 
the case of hydrogen being the evolved gas ? 

Why should the tube leading from the flask go to the bottom of the 
Winchester, and that which leads out of it come from the top ? 

What relationship must there be between the volume of the 
Winchester and the volume of gas evolved ? 


' 


112 TEXTILE CHEMISTRY 


Perform the experiment at least twice and take the average of the 
results if they are nearly identical. 

Carbon monoxide or carbonic oxide is the lower oxide of carbon. 
It is of considerable industrial importance, being used in metallurgical 
operations, reverberatory furnaces for reducing purposes, as an 
adulterant for coal gas, etc. 

Methods of Preparation :— 
1. Pass carbon dioxide over heated carbon (Fig. 165). An iron 


tube should be used, and the stream of carbon dioxide should be a 
slow one. 

The same preparation goes on in a clear fire (Fig. 166). The carbon 
dioxide first formed is reduced in the centre by the hot coke to carbon 
monoxide, which then burns to produce the 
dioxide again. 

2. Pass air over strongly heated coke or 
anthracite. A mixture of carbon monoxide and 
nitrogen is obtained, known commercially as 
“ generator ’”’ or “ producer ”’ gas. 

3. Pass steam over red-hot anthracite or coke. 
A mixture is produced known as “ water gas.” 
This gas, which has an average composition of 
50 per cent. hydrogen, 40 per cent. carbon mon- 
oxide, 5 per cent. carbon dioxide, and 5 per cent. 
nitrogen, is used largely as gaseous fuel and as a 
reducing agent. It can be made very luminous by mixing it with a 
very small proportion of unsaturated hydrocarbons, and in this form 
it is used in America in lieu of coal gas. 

4, From formic acid, by heating it with strong sulphuric acid. The 
former can be looked upon as a compound made up of water (H,O) and 
carbon monoxide (CO). Hot sulphuric acid abstracts the water and 
liberates the gas. 


CARBON MONOXIDE 113 


5. The usual lecture preparation is from oxalic acid and strong 
sulphuric acid (Fig. 167). 

Oxalic acid may be looked upon as being composed of water (H,0), 
carbon dioxidé (CO,), and carbon monoxide (CO). When heated with 
strong sulphuric acid, the water is abstracted and both oxides of 
carbon are liberated. The dioxide is scrubbed out by passing the 
mixture through two wash bottles containing baryta water, and then 
through two containing strong caustic soda solution. 

The gas is present in coal gas in small quantity, in the vapour 
evolved from lime kilns, and in blast furnace gas. It is produced at-all 
times when carbon is burnt in an insufficient supply of air—hence 
*‘ slow combustion ”’ stoves, such as are often met with on the Con- 
tinent, are liable to emit it, and many fatal accidents have occurred 
due to defective ventilation in connexion with their use. Zola’s 
death was due to this cause. 


Ba(OH), NaOH 


PROPERTIES 

It is a colourless gas, tasteless. and practically odourless; very 
slightly soluble in water, and a little lighter than air. It is extremely 
poisonous—l1 per cent. in air is fatal to human beings. It burns with 
a blue lambent flame, the temperature of which is 1,400°C., to 
form carbon dioxide; it does not support combustion, and has no 
action on lime water or litmus paper. 

It explodes when mixed with an equal volume of air or half its own 
volume of oxygen, and is extremely difficult to liquefy. 

It acts as a powerful reducing agent at high temperatures. It is 
absorbed by a solution of cuprous chloride in hydrochloric acid (Fig. 
168). The gas is delivered up the Crum tube and a solution of cuprous 
chloride passed from the cup a few drops at a time. As the gas is 
absorbed, the mercury rises. 

It unites directly with certain elements, for example nickel, potas- 


8 ; 


114 TEXTILE CHEMISTRY 


sium, and iron, to form carbonyls. The carbonyl of chlorine, COCI,, is 
known as phosgene gas, which on exposure to moist air forms hydro- 
chloric acid gas and carbon dioxide. It was used in the Great War 
as a “‘ poison” gas. 

Marsh gas or methane is a gas which is produced by the decay of 
vegetable matter, particularly in swampy districts. A sample may be 
collected often from a stagnant pool by piercing the bottom mud with 
a stick. The bubbles of gas as they reach the surface may be ignited. 
A large percentage of coal gas is methane. 

It is prepared usually for experimental purposes by heating a 
mixture of fused sodium acetate and soda lime in a test tube provided 
with a collar of wire gauze, to prevent cracking the glass (Fig. 169). 


F1G.168 


The gas produced will be found to be lighter than air, and to burn 
with a fairly luminous flame to form water vapour and carbon dioxide. 
It is also explosive when mixed with air or oxygen. 

Analysis of the gas shows that it is composed of hydrogen and 
carbon only ; it is therefore termed a hydrocarbon. The proportion by 
weight in which the constituents exist is 12 of carbon to 4 of hydrogen ; 
the “ picture ’’ of the molecule is thus given as :— 


H 


H—C—H or CH,. 


| 
H 


HYDROCARBONS 115 


By other chemical reactions it is possible to prepare or isolate from 
natural substances, like crude rock oil, other hydrocarbons, e.g. ethane, 
propane, butane, pentane, hexane, etc., and analyses of these com- 
pounds show that their molecular compositions are represented by the 
formule C,H,, C;H;, C,H,., Cs;Hi., C.Hi4, etc., the increases 
in molecular weights being identical (CH.). Such a series of com- 
pounds is known as an homologous series, and the graphic formule used 
to represent them are derivable from marsh gas by substitution of the 
CH, or methyl group in place of the hydrogen atom at the end of the 
chain. 7 


H H in fds Bagel H H HH 

HCOOH H-C-C-0-H H-C-¢-C-C-H, ete 

ee hk HH HH 

Theoretically, there will be an infinite number of possible hydrocar- 
bons of this series ; as a matter of fact a very large number has been 
isolated from American rock oil, which is, to all intents and purposes, 
a mixture of them. 

When the crude petroleum is fractionally distilled—that is, heated 
to a gradually increasing temperature, the distillates being carefully 
collected separately as they are evolved at the various temperatures 
—first gases,.then liquids of low boiling-points, and then liquids 
of higher boiling-points are obtained which are used on an enor- 
mous scale in everyday life, as petrol, paraffin, lubricating oils, 
salves, etc. 

These fractions, known as mineral oils, are all mixtures of 
hydrocarbons of the paraffin series (as it is termed), the first con- 
taining the lower members of the series, and the latter the higher 
ones. 

They are very stable and inert substances, resisting the action of 
most chemical reagents, particularly acids and alkalis; consequently 
a mineral oil stain is very difficult to remove from a fabric. 

In Scotland (and, it is now claimed, in some parts of England) 
certain shale deposits when distilled in a similar manner yield 
similar oils, the residual portion of which is known as paraffin 
wax. 

The great Russian deposits contain benzoline or benzine, a mixture 
of higher members of the same series. Coal tar yields benzene (C,H), 
a hydrocarbon which cannot be correctly represented as an open chain. 
Kekulé suggested that carbon and hydrogen were arranged as a 
ce ring 9 me 


\ 


116 TEXTILE CHEMISTRY 


Benzene, C,H,. 


Benzene and other hydrocarbons of the same series are obtained 
from the destructive distillation of coal tar, e.g. naphthalene and 
anthracene :— 


Naphthalene, C,,H;3. 


jee seh 3! 
6 b 6 
AG 
H-C GC CG C—H 


ele ae 
H—O. | C:2 Cages 


AZ Dae 
C C C 
Been | 
He) RE 

Anthracene, C,¢H4o. 


COMPOUNDS OF CARBON 117 


Naphthalene is used as the starting-point in the synthetic prepara- 
tion of indigo in one important process, and anthracene is the raw 
product from which is manufactured alizarine (the active colouring 
principle in madder), used in Turkey red dyeing. 

Other hydrocarbons are known, e.g. acetylene and ethylene, which 
are considered to be “ unsaturated ’? compounds. 


H H 

foe -H ee 

Acetylene, C,H. H H 
Ethylene, C,H,. 


Substitution Compounds 

“‘ When methane is mixed with chlorine and exposed to sunlight, 
a violent reaction occurs, but when the chlorine is diluted with carbon 
dioxide, and allowed to act gradually, chlorine substitution products 
are obtained.” — 

An analysis of these compounds shows that their molecular com- 
position is represented by the formule :— 


CH,Cl Mono-chloro-methane. 

CH.Cl, Di-chloro-methane. 

CHCl,  Tri-chloro-methane (chloroform). 

CCl, Tetra-chloro-methane (carbon tetrachloride). 


It is evident that these compounds are methane in which the 
hydrogen has been replaced by chlorine ; in other words, a substitution 
has taken place :— 


H oe ie ie 
alee Se Cl nce Cl Gr apaes 
cl AC 


Chloroform is not yet prepared by this process commercially, the 
usual way being to act on bleaching powder with ethyl alcohol and 
distil the mixture on a water bath (Fig. 170). 

Suitable quantities to use are 180 grams of bleaching powder, 400 
c.c. of water, and 11 c.c. of alcohol in a one-litre flask. The heating 
must be gradual, and there is considerable frothing. The distillate 
contains alcohol and water as well as chloroform, which settles to the 
bottom of the mixture. 

The sp. gr. of chloroform is 1-5, and its boiling-point is 61:5° C. 


118 TEXTILE CHEMISTRY 


Alcohols. This class of compounds can be looked upon as 
hydroxyl (O—H radicle) substitution products of the hydrocarbons, 
&.g.i— 


H H H 
ae ioe Pa a, are 
Ha? Nee ee 
Methyl alcohol, CH;,0H. Ethyl alcohol, C,H,OH. 


Again we find an homologous series. More than forty alcohols were 
prepared by Dr. R. H. Pickard, F.R.S., 
and his research assistants in the 
chemical laboratories of the Blackburn 
Technical College a few years ago. 

Methyl alcohol, also known as 
wood spirit, and wood naphtha, is 
obtained in the destructive distilla- 
tion of wood and beetroot sugar 
refuse. Its chief uses are as a sol- 
vent for gums and resins in the 
varnish industry ; in the preparation 
of coal-tar dyes; and as an adulterant 
of ethyl alcohol, in the preparation 
sold as methylated spirit. 

Ethyl alcohol, or ordinary alcohol, 
is prepared by the fermentation of 
sugar, the weak solution thereby 
produced being fractionally distilled. 
Boiling-points Methyl = 66°C. 

Ethyl = 78-3° C. 
Specific gravity (at ordinary tem- 
peratures) Methyl = 0-793 
Ethyl = 0-8 

Amyl alcohol or fusel oil is a mixture of two or more alcohols higher 
in the series than ethyl alcohol. : 

Glycerol (glycerine) is also an alcohol, and contains three hydroxyl 
groups—C,H ,(OH);. 

Cetyl alcohol, C,,H3;;0H, is present in spermaceti wax. Chinese 
wax and beeswax contain alcohols higher still in the fatty series. 

Phenol (commonly known as carbolic acid) is a compound of the 
benzene series which resembles an alcohol in some respects :— 


COMPOUNDS OF CARBON 119 


| | or C,H,OH. 


Ethers. This class of organic compounds is analogous to oxides, 
the basic radicle being replaced by one or more hydrocarbon radicles, 
e.g. — 

H H 


| | 
a or (CH;),.0, methyl ether. 
| 
H H 

(C.H;).0, or ethyl ether, i.e. ordi- 
nary or sulphuric ether. 

CH,.0.C.H;, or methyl ethyl ether. 

The two latter may be prepared by 
what is known as the continuous etheri- 
fication process. Ethyl alcohol or 
methylated spirit is carefully run into 
half its own volume of strong sulphuric 
acid, without allowing the temperature 
to rise unduly. It is then distilled at 
a temperature of 140° C. (in the liquid), 
a slow stream of alcohol or methylated 
spirit being passed in as the ether 
distils off (Fig. 171). 

Ether gives off dangerously inflam- 
mable vapour, and great care should 
be taken to keep flames away from it. 
Bottles of ether should be kept on the floor 
and never on a laboratory bench. Very 
disastrous consequences have occurred 
due to inattention to this simple precau- 
tion. 
Ethyl ether, sp. gr. at 15°C. = 0-7; 
b.p. = 35°C. Ethyl ether dissolves in 


120 TEXTILE CHEMISTRY 


ten times its own volume of water, and is miscible with alcohol and 
other organic liquids in all proportions. 

Chief Uses. As a solvent for fats, oils, resins, etc., and as an 
anesthetic in surgery. 

Aldehydes. When a slow stream of air is passed through methyl 
alcohol some of it vaporizes; and if the gaseous mixture be passed 
over heated copper gauze, and then the product so formed into water, 
it will be found that a solution is obtained which has very characteristic 
properties (Fig. 172). It has a pungent smell, will reduce an ammoni- 
acal solution of silver nitrate (oxide) to metallic silver, and will 
restore the colour of Schiff’s reagent, which is made by decolorizing a 
dilute solution of magenta in water, with a stream of sulphur dioxide. 

This solution is known as formalin, and it is possible to make it of 
40 per cent. strength, in which condition it is usually sold. 


It is used in large quantities in the manufacture of artificial dyes, 
and as an antiseptic. 

The gas is termed formaldehyde, and it has been found to have the 
composition 2 parts by weight of hydrogen, 12 of carbon, and 16 of 
oxygen; in other words, there are 2 atoms of hydrogen, 1 atom of 
carbon, and 1 of oxygen in the molecule, (or graphically) 


H—C=0 


| 
H 


Other compounds exhibiting similar properties and containing the 
radicle CHO have been prepared ; and as they apparently are alcohols 
which have been deprived of two atoms of hydrogen, they are named 
aldehydes (Alcohol dehydrogenatum). The name Form indicates that 
on further oxidation the acid so obtained is formic. 

The next member of the series is Acetaldehyde. Benzaldehyde, 
or artificial oil of almonds, or (in the crude form) oil of mirbane, is the 
simplest benzene aldehyde, C,H,CHO. 


ACIDS OF CARBON 121 


Acids. Hundreds of carbon acids have been prepared and their 
compositions investigated, and as a result it is firmly established that 
they all contain the monovalent group COOH, termed the carboxyl 
radicle. The lowest member of the paraffin series is formic acid, 
H.COOH, the next is acetic acid, CH,COOH. 

When these acids react with alkalis to produce salts, it is the 
hydrogen in the COOH group which is replaced by the metallic base, 
e.g. :— 


Sodium formate : : . H.COONa. 
Potassium acetate f ‘ obs CUOKS: » 
Calcium acetate ; ; . (CH;.COO) Ca. 


Oxalic acid is termed a di-basic acid because it contains two 
carboxyl groups. Its formula is written (COOH).. 


Sodium oxalate is therefore (COO) ,Na.. 
Calcium oxalate, (COO) Ca. 
Other important acids are :— 


Butyric acid C,H,.COOH (in butter fat). 
Palmitic acid C,;H;,.COOH (from palm oil). 
Oleic acid C,,H;;.COOH (from olive oil). 
Stearic acid C,,H;;.;COOH (from tallow). 


Note.—Fats are salts of the “fatty acids,” in which the hydrogen 
of the carboxyl group has been replaced by the tri-hydric alcohol 
glycerol, instead of a metal. Thus :— 

From oleic acid (3 molecules) From glycerol 
(C,,H33.COO); == == O,H;,. 

For the preparation of these fatty acids, the fat is first saponified 
by boiling it with caustic soda or potash. Double decomposition 
occurs, the alkali salt of the acid being formed (which is known as a 
soap), together with glycerol. 

The soap can then be hydrolyzed by the addition of a mineral acid, 
another double decomposition resulting with the formation of the 
fatty acid (often insoluble in water) and the production of the alkali 
salt of the mineral acid. 

As fats always contain more than one glyceride, although one is 
usually in excess, further manipulations are necessary if a pure fatty 
acid is required. 

Acetic acid is prepared by three processes :— 

(a) Fermentation of dilute alcoholic solutions containing small 
amounts of nitrogenous and phosphatic food-stuffs, such as beer or 
light wines, by the microscopically small plant named Mycoderma 
aceti or mother of vinegar. 


122 TEXTILE CHEMISTRY 


(b) By the quick vinegar process. A large vat (Fig. 173) is made 
into three compartments by means of two grids, the space between 
being filled with beech shavings. Holes are bored at intervals in the 
sides of the barrel to allow air to enter. 

In the top compartment A vinegar is put, which slowly drops into 
B by travelling down the pieces of string that hang through the holes 
in the top grid. The shavings thus become covered with Mycoderma 
acett present in the vinegar. 

Dilute alcohol is now put into A, and it ultimately finds its way into 
C, from which it siphons off at intervals. After two or three passages 
the alcohol is completely oxidized to acetic acid. 

(c) From pyroligneous acid, obtained by the destructive distillation 
of wood. Soda ash is added to the crude distillate to produce sodium 
acetate, which is crystallized out, purified 
aN by recrystallization, and then fused. 

The fused sodium acetate is then 


f =k \ treated with strong sulphuric acid and 
OSS ae distilled, when acetic acid is evolved. 

( ey A | This is further purified by freezing out 

\ a Nee “t the acetic acid. 


Anhydrous acetic acid has a m.p. of 
16-5° C. and a b.p. of 118° C. 

Oxalic acid may be prepared by 
oxidizing cane sugar (1 part) with strong 
nitric acid (6 parts) ; and a modification 
of this process is used industrially for 
nearly the whole production of oxalic acid. 

Sawdust is made into a paste with a strong solution of a mixture of 
equal parts of caustic soda and caustic potash, heated in iron pans to 
210° C.; the mixed oxalates of sodium and potassium are extracted 
with water, and boiled with lime. The resulting calcium oxalate is 
decomposed with dilute sulphuric acid, separated from the calcium 
sulphate, concentrated, and crystallized. 

Formic acid is prepared by heating a mixture of oxalic acid 
and glycerine and condensing the distillate ; a temperature of 110° C. 
should be maintained whilst the process is in operation. 

Formic acid is being used very considerably in the textile industry 
to-day, and with great success. | 

Carbohydrates (so called because the ratio of hydrogen to 
oxygen found in them is the same as that in water) form a class of 
compounds of complicated chemical structure, the nature of which is 
not yet thoroughly known. 

There are two groups :— 


CARBOHYDRATES 123 


1. Sugars: (a) The glucoses (C,H,.0.),.- 

(b) The sucroses or cane sugar (C,,H,,0,)). 

2. Starches and cellulose (C,.H,,0;). 

Glucose, grape sugar, or dextrose, C,H,,0,, occurs naturally in fruits 
and honey, and is also prepared industrially in large quantities from 
starch. One method in use is to raise to boiling-point water containing 
1-5 per cent. sulphuric acid. 

Into this is then run gradually a mixture of starch and water, and 
boiling is continued for half an hour. The mixture is neutralized with 
chalk, and concentrated, the calcium sulphate being precipitated. The 
clear syrup is further concentrated in vacuum pans until it is a thick 
viscous liquid or a solid. 

It contains about 70 per cent. glucose, about 30 per cent. maltose, 
dextrine, and calcium salts of organic acids. 

If the presence of a small quantity of salt be not objected to, 
hydrochloric acid may be used instead of sulphuric, and the neutrali- 
zation effected with sodium carbonate ; the boiling should be continued 
for at least an hour. 

A much purer substance can be obtained by boiling cane sugar with 
dilute acid (see invert sugar). | 

Glucose is less sweet than cane sugar. Its solubility is: 10 in 12 
of cold water ; 1 in 50 of cold alcohol; 1 in 5 of boiling alcohol. It is 
not blackened easily when treated with strong sulphuric acid, and it is 
immediately fermented by yeast. 

It is used for making alcohol, in confectionery and jam, and by 
dyers and calico-printers as a thickening ingredient. 

Cane sugar, C,,H..0,,, is the most important of the naturally 
occurring sugars, and forms an essential article of human diet. Many 
vegetables and plants contain it, some in sufficient quantities to pay to 
extract it, e.g. sugar cane, maple tree, beetroot. 

It is very soluble in water, dissolving to the extent of 67 in 23 at 
20° C., and to almost any degree in hot. It is insoluble in alcohol, 
fuses at 160°C., and does not crystallize on cooling. It is readily 
blackened by strong sulphuric acid, and is very sweet. It is not fer- 
mentable by yeast until changed to glucose, and does not reduce 
Fehling solution. 

Levulose is found in many ripe fresh fruits and in honey ; it is some- 
times known as fruit sugar. It is much sweeter than glucose and 
nearly as sweet as cane sugar. 

Honey is a mixture of one-half levulose, one-third to one-half 
dextrose, and some cane sugar. The former is soluble in cold alcohol, 
and dextrose in boiling alcohol. 

Lactose or milk sugar, C,,H,,0,,.H,O, is present in milk, and can 
be obtained by concentrating and crystallizing the whey. Cow’s milk 


124 TEXTILE CHEMISTRY 


contains 4:7 per cent. When heated to 130° C. the water of crystalli- 
zation is evolved. It is sweeter than cane sugar, but less soluble, e.g. 
1 in 6 of cold water, 1 in 2:5 of hot water, and insoluble in alcohol. 

Maltose, C,,H,.0,,;.H.O, is formed from starch by the action of a 
ferment, diastase, produced when barley germinates. Grain containing 
this ferment is known as malt. The best temperature for the conver- 
sion of starch into sugar by malt is 65° C. Its chief use is as a ferment- 
able sugar in the preparation of alcohol, as it very readily ferments 
with yeast. It is less soluble in alcohol than dextrose. 

Suitable formula for its preparation : Into 350 c.c. of boiling water 
run 100 grams of starch completely mixed with 100 c.c. of cold water, 
and stir well. When the temperature has fallen to 65° C., add 7 grams 
of crushed malt, and keep the mixture at 65° (on a water bath) for one 
hour. At the end of that time test for sugar and starch. When 
maltose is boiled with dilute acids it is converted into glucose. 

Invert sugar contains equal quantities of dextrose and levulose. It 
can be prepared by dissolving cane sugar in water, adding a little 
sulphuric or hydrochloric acid, and keeping on a water bath for half 
an hour at 100°C. 

The acid is neutralized by addition of barium carbonate or caustic 
soda, and evaporated to a syrup. <A great deal of artificial honey is 
prepared in this manner. 

Starch, (C,;H,,0;),, is a carbohydrate of universal distribution in 
vegetable tissues (see pages 184-188). It is insoluble in most solvents 
in the cold, but when boiled with water and solutions of certain 
chlorides, etc., it forms colloidal solutions which on cooling set as 
** jellies.” 

Boiled with dilute acids it is converted into sugar. Heated with 
strong sulphuric acid it is “‘carbonized.” It is decomposed in a 
similar manner when heated alone in the dry condition. 

The reaction for the identification of starch is that of iodine, which 
forms a compound with it that gives a deep blue colour on dilution 
with water. 


SECTION XI 
CHLORINE 


HLORINE is a greenish gas which is very readily obtained 
from hydrochloric acid. Scheele, who first prepared it in 1774 


from this acid and manganese dioxide, named it dephlogisti- 
cated marine acid air, a name which was changed some forty years 
later by Davy to chlorine, on account of its greenish-yellow colour. It 
is an element. 


fig75 


It is still prepared chiefly by the original method, although many 
peroxides heated, with hydrochloric acid will evolve the gas. 

A convenient apparatus for its preparation on a small scale is 
shown in Fig. 174. A and B are wash bottles containing water; C 
is a tube containing calcium chloride to dry the gas. 

Reaction: MnO, + 4HCl = MnCl, + 2H,0 + Cl;. 
It may also be obtained from many chlorides by heating with 
| 125 


126 = TEXTILE CHEMISTRY 


strong sulphuric acid and a peroxide. With common salt the reaction 
is :— 

2NaCl + 2H,SO, + MnO, = Na.SO, + MnSO, + 2H,O + Cl,. 

When a strong solution of hydrochloric acid is electrolyzed, chlorine 
is evolved at one electrode (Fig. 175). 

It can also be obtained by heating hydrochloric acid with either 
potassium dichromate, potassium chlorate, red lead, or bleaching 
powder. 

Before collection, which may be by displacement of air or over 
strong brine, the gas should always be washed through water to collect 
any hydrochloric acid that may be carried over. 


SOME CHEMICAL PROPERTIES 
1, A jet of hydrogen or coal gas burns in a jar of chlorine to produce 
hydrochloric acid (Fig. 176). 
2. A solution of chlorine in water exposed to sunlight gradually 
loses its colour, liberates oxygen, and forms a solution of hydrochloric 
acid (Fig. 177). 


— 


FIG176 f1G.177 | Figi7s 


3. Mix chlorine water and ‘sulphuretted hydrogen solution: sulphur 
is deposited and hydrochloric acid is produced. 

4, When phosphorus (on a deflagrating spoon) is placed in a jar 
of the gas it melts, spontaneously inflames, and produces fumes of 
phosphorus chloride. | 

5. Burning sodium in it produces a white deposit of common salt. 

6. It bleaches moistened vegetable-coloured articles, due to libera- 
tion from the water of ‘‘ nascent ” oxygen, which oxidizes the colouring 
matter. 

Cl, + H,O = 2HCl + O. 


Note.—Perfectly dry chlorine will not bleach. 
7. It attacks mercury. 


rn 


CHLORINE 127 


8. It unites with hydrogen in daylight to form hydrochloric acid. 

9. Finely powdered metals like antimony, iron, copper, burn when 
dropped into chlorine, particularly if they are warm. 

10. It combines with hydrogen present in hydrocarbons, such as 
turpentine, to form hydrochloric acid. The energy of combustion is 
usually sufficient to inflame the rest of the turpentine. 

11. Note effect of the gas on a solution of potassium iodide. Iodine 
is liberated, which in the presence of starch produces a blue compound. 


PHYSICAL PROPERTIES 
Irritating odour; green colour; 1 litre at N.T.P. weighs 3-1645 
grams; 24 times as heavy as air; fairly easily liquefied ; soluble in 
water to a moderate degree. 
Chief Uses. As a bleaching agent for cotton goods ; a disinfectant 
and deodorizer; for preparation of chlorides and other compounds 
containing chlorine ; for extraction of gold from quartz. 


LABORATORY EXERCISES 


Fit up the apparatus as shown in the diagram (Fig. 178). In the 
flask put some commercial hydrochloric acid and manganese dioxide. 
Thoroughly mix and then gently warm. 


Collect two or three samples of the gas in dry gas jars. 

Is the gas heavier or lighter than air? Is it combustible? Will 
it support combustion (a) of an ordinary light ? (6) of turpentine on 
filter paper ? (c) of phosphorus (not previously ignited) ? (d) of sodium 
(ignited first) z 

Drop in a few grains of powdered antimony and describe what 
happens. 

Test its action—wet and dry—on litmus paper and Turkey red 
cloth (Fig. 179). 

Prepare a solution of the gas in water, describe its colour and smell. 


Lon TEXTILE CHEMISTRY 


Pass the gas into a few c.c. of a fairly strong solution of caustic soda. 
Note what happens when dilute acid is added to the product formed. 

Pass the gas through slaked lime, using the apparatus shown in 
Fig. 180. Study the effect of adding an acid to the substance produced. 

On the commercial scale at the present day chlorine is prepared : 
(1) By the original Scheele method; (2) by the Deacon process ; 
(3) by electrolytic methods ;—of which the first is the most important. 

In the first method the reaction vessel is made of stone slabs, luted 
and bound together by iron bands, and is known as a chlorine still 
(Fig. 181). 

Manganese dioxide is spread on a raised wooden floor, the acid being 
fed in through a funnel which dips into a bowl placed on this floor, 
over which it gradually flows. 


fig. 182. 


Here manganic chloride is formed as a dark brown liquid. Steam 
is then passed in under the wooden floor of the still, with the result 
that the higher chloride of manganese is decomposed to form the lower 
manganous chloride, with liberation of chlorine. 

This process would not be a commercial success unless the man- 
ganese could be ‘“‘ recovered.” ‘This is done by the Weldon process. 
Fig. 182 shows the principle of this method. 

The still liquor is neutralized with chalk in A. It is then pumped. 
to the settling tank B, from which the supernatant liquid (which 
contains manganous chloride and calcium chloride) is run at intervals 
into the oxidizer C. 

Here it is mixed with milk of lime from D, the temperature raised 
to 50° C. by blowing in steam, and finally air is blown through. This 
produces an insoluble compound of calcium and manganese, CaOMnO, 


CHLORINE 129 


or Ca02MnO,, which can be again treated with hydrochloric acid 
to yield chlorine. 

For this purpose the contents of C are run into settling tanks EH, 
where the precipitate settles as a paste known as Weldon mud. After 
the supernatant liquid has been decanted off the residue is passed into 
the chlorine stills. 

The Deacon process can be illustrated by using the apparatus shown 
in Fig. 183. Hydrochloric acid gas is generated in flask A from salt 
and sulphuric acid, oxygen is passed from aspirator O, and both gases 
are dried by passage through strong sulphuric acid in bottle B. They 
then pass through the hard glass tube C, containing heated cuprous 
chloride, in contact with which the dry hydrochloric acid is decom- 
posed, hydrogen combining with oxygen, and chlorine being liberated. 
By passing the product through D, the water can be absorbed and dry 
chlorine collected in the gas jar. 


iv 


FiG.133 ) 


To Tap 


Owing to technical difficulties in working the process, the method has 
not developed to the extent that was once thought possible. 

One of the most successful methods for the electrolytic preparation 
of chlorine is that of Castner (Fig. 184). 

The reaction chamber is divided into three cells by two vertical 
partitions which go nearly to the bottom, along which is spread a thin 
layer of mercury. The two outside compartments, which are dupli- 
cates, contain carbon electrodes, and the centre compartment an iron 
one. When the current is passed, the solution of sodium chloride in 
the outside compartments is decomposed with liberation of chlorine 
(which leaves the chamber by means of the pipes) and sodium which 


9 


130 TEXTILE CHEMISTRY 


dissolves in the mercury. The sodium amalgam thus formed is now 
sent into the centre compartment by rocking the cell, where it is 
decomposed by the water therein, thus producing a solution of caustic 
soda with liberation of hydrogen. As soon as the apparatus is rocked 
in the opposite direction the mercury passes back into the outside 
compartment to be used over again. ‘The rocking action is made 
automatic by arranging one end of the cell on a pivot, and the other 
on an eccentric, with the motion of which the end resting on it gradually 
rises and falls. 

Hypochlorites. If a stream of chlorine gas be passed into a 
solution of cold caustic soda or caustic potash, the gas is absorbed ; 
and if the product be treated with very dilute acid and distilled under 
reduced pressure and at a low temperature, a solution is obtained which 
contains a very unstable acid called hypochlorous acid, the composition 
of which is represented by the formula HClO. 


ee Ui treacascosaee Li eae 
aN ee 


It is a salt of this acid which is produced, together with the alkali 
chloride, when chlorine is absorbed by cold caustic soda or potash. 


Cl, + 2KOH = KCl + KOCI + H.O. 


This substance was prepared as long ago as 1785 by Berthollet, and 
called Eau de Javelle, from the name of the suburb of Paris where it 
was made in 1792. When Labaraque discovered in 1820 that a similar 
reaction occurred with caustic soda, the liquid was made from it instead 
of the more expensive potash, and sold under the name of Eau de 
Labaraque. 

The most striking property of these hypochlorites, even in very 
dilute solution, is their power of bleaching—which is much more pro- 
nounced than with chlorine alone; this has been attributed-to the 
liberation of hypochlorous acid, which is a bleaching agent, due to the 
fact that it very easily splits up into igs acid and nascent 
oxygen. 


CHLORINE 131 


In 1798 a process was patented by Tennant for using lime instead 
of potash, the patent rights of which were subsequently revoked 
because it was proved that this “ bleaching powder ” had been pre- 
viously in use in Lancashire. This substance is not calcium hypo- 
chlorite : what it really is has been the subject of much discussion. 
The most generally accepted view is that if pure it is a compound 
intermediate between calcium hypochlorite and calcium chloride, 
named calcium chloro-hypochlorite, the composition of which is given 
by the formula Ca(OCl)Cl. This on treatment with water yields both 
calcium chloride and calcium hypochlorite. 


2Ca(OCl)Cl = Ca(OCl), + CaCl. 


Bleaching powder, sometimes incorrectly called chloride of lime, is 
made in large chambers, the floors of which are covered with a layer of 
fresh-slacked lime about four to six inches deep, raked into furrows to 
expose a greater surface. Chlorine straight from the chlorine stills is 
passed in until the gas is no longer absorbed. The excess is removed 
by blowing in a little powdered lime, and it is then collected and packed 
in barrels. 

Sodium hypochlorite, for which there is now a considerable demand, 
is prepared electrolytically as well as by direct absorption of chlorine 
by caustic soda. 

The liquid used is a solution of salt in water, the strength varying 
with the strength of the current. The electrodes are of carbon, anda 
constant circulation is kept up in the cell, so that the chlorine liberated 
at one electrode shall be absorbed by the caustic soda formed at the 
other. ‘This process is described in greater detail under “‘ Bleaching ”’ 
(Section XVI, pages 205-213). 

An emulsion of bleaching powder mixed with a solution of sodium 
carbonate also produces sodium hypochlorite and calcium carbonate. 
The latter may be sedimented or filtered off, and a solution of the former 
obtained. 

Made by the last process the liquid contains dissolved lime. When 
prepared by means of the electric current it is, or should be, neutral, 
and when prepared in the original way it is strongly alkaline, due to the 
presence of free soda. 

Besides being used for bleaching purposes under various trade 
names such as Parozone, Lavozone, etc., it is also used as a germicide 
(in which capacity it is highly efficient) as Chloros, Milton, etc., and 
as a “softening ” preparation for size, under the name of Paetchner’s 
solution. | 

The most suitable laboratory method for preparation of the liquid 
is to pass chlorine through 20 per cent. caustic soda solution till no 
more gas is absorbed, using the apparatus shown in Fig. 185. 


132 TEXTILE CHEMISTRY 


Sulphur dioxide (SO,). Several oxides of sulphur are known, 
of which the dioxide is by far the most important. 

It is obtained by burning sulphur in air or oxygen. Besides 
this method there are other ways by which the gas may be pre- 
pared :— 

1. The usual laboratory method. Act on certain “ heavy ” metals 
with strong hot sulphuric acid. In this case the oxide is liberated from 
the acid, and a metallic sulphate and water are formed. The metals 
which will give this reaction are copper, mercury, silver. Copper, being 
the cheapest, is used. 

To prepare the gas, set up the apparatus shown in Fig. 186. 

2. From sulphides by roasting in a current of air or oxygen, e.g. 


Fig. 186 


iron pyrites, copper pyrites, cinnabar. The metal is converted in part 


or entirely into the oxidein most cases. This isa very general metal- 
lurgical method adopted for freeing ores from a quantity of their 
sulphur. . 

3. By heating sulphur with certain peroxides, e.g. manganese 
dioxide, or with sulphuric acid, the acid being thereby reduced. 

4. By decomposing the class of salts known as sulphites, e.g. 
sodium sulphite, or sodium bisulphite, with dilute acids. 


PROPERTIES 
Colourless. (The so-called white fumes of sulphur dioxide are 
due to traces of sulphuric acid and sulphur trioxide that are sometimes 
formed.) Suffocating smell (minute traces of the gas breathed for a 
short time appear to be beneficial rather than harmful). It is non- 
combustible, and will not support ordinary combustion, but if sodium 


SULPHUR DIOXIDE 133 


peroxide be dropped into a jar of the gas a few grains at a time, brilliant 
combustion results. 

It is somewhat heavy (more than twice as heavy as air), and soluble 
in water to form an acid solution known as sulphurows acid. 


1 volume of water at 0° C. dissolves 80 volumes of sulphur dioxide. 
1 o> 99 20° C. 93 39 > 9% 3? 
1 >) 99 40° C. 39 19 9) 99 39 


Boiling expels all the gas. 

It is easily liquefied by pressure (and so comes into commerce in 
glass siphons and iron bottles), and by cooling (Fig. 187). 

Pass the previously dried gas into a small bottle surrounded with a 
freezing mixture of salt, ice, and calcium chloride. 

Inquid sulphur dioxide is a fairly mobile liquid: poured into water 
it freezes it, due to rapid evaporation. At 0° C. a pressure of 14 atmo- 
spheres condenses the gas to a liquid. At ordinary pressures a tem- 
perature of — 10° C. condenses it. It dissolves 
phosphorus, iodine, resins, etc. 

Uses. Sulphur dioxide is largely used as 
a bleaching agent for goods which must not 
be bleached by chlorine, e.g. straw, silk, sponge, 
flannel, blankets, and wool articles generally. 

Its action in bleaching is due to the gas 
decomposing the water, which must be present, 
to form sulphur trioxide, thereby liberating 
hydrogen, which reduces the colouring to a 
more or less colourless compound. 

Alkalis often restore the colour, e.g. flannel 
which has been well washed with soap returns to its original yellow 
colour. 

The gas is used for fumigating purposes, and in the liquid state it 
finds application as a refrigerating agent. 

The best test for the identification of sulphur dioxide is its action 
on potassium chromate paper or solution, which it turns green. 

Hydrogen peroxide, H,O,. Only two compounds of hydrogen 
and oxygen are known—water and hydrogen peroxide, which may 
be looked upon as oxide of water. 

It is prepared by the action of several acids on barium peroxide, 
e.g. carbonic, hydrochloric, sulphuric, phosphoric, and hydrofluoric. 
In all cases the temperature must be kept low enough to prevent the 
decomposition of the hydrogen peroxide formed. If made with 
sulphuric acid, the acid must be diluted considerably. 

On the commercial scale it is often prepared with the aid of phos- 
phoric acid, but for laboratory purposes the best results are obtained 
by using hydrofluoric acid. 


134 | TEXTILE CHEMISTRY 


A well-made cigar box should be soaked in hot paraffin wax, and 
then coated with a layer of that substance ; a suitable wooden stirrer 
should be treated in the same way. 

The box should be partly filled with ordinary hydrofluoric acid 
diluted with four or five times its own volume of water. Barium 
peroxide is fed in with constant stirring until the liquid is no longer 
acid. The precipitate of barium fluoride is allowed to settle, when a 
strong solution of hydrogen peroxide will be found in the supernatant 
liquid. 

Sodium peroxide may also be used, the reaction with hydrochloric 
acid being— 


Na,O, + 2HCl = 2NaCl + H,0,. 


The aqueous solution obtained as above is concentrated in vacuo, 
over strong sulphuric acid. It comes into commerce labelled 10 
volumes, 20 volumes, etc., which means that when treated with acidified 
potassium permanganate, 1 volume of solution yields 10 or 20 volumes 
of oxygen. (N.B.—Half of this, however, comes from the perman- 
ganate) :— 


K,Mn,0, + 5H,0, + 3H,SO, =~ K.SO, + 2MnSO, ate 8H,O = 5O,. 


PROPERTIES 

In the pure condition it is a colourless, odourless, syrupy liquid, of 
very bitter taste, sp. gr. 1-45, and very unstable. 

Diluted with water, in which condition it is usually met with, it is 
a very active oxidizing substance, and a powerful bleaching agent, 
e.g. :— 

PbS + H,O, = PbSO, + 4H,O (the reaction which occurs when 
it is used to “restore”’ oil paintings). 

H,O, + H, = 2H,0 (hydrogen oxidized to water). 


LABORATORY EXERCISES IN THE PREPARATION AND ESTIMATION OF 
HYDROGEN PEROXIDE 


1. Preparation. Weigh out about 30 grams of barium peroxide. 

To 40 c.c. of “ bench ” dilute sulphuric acid add 160c.c. of water. 
Stir into this the barium peroxide, a gram or so at a time, keeping the 
temperature from rising. When all has been added, allow it to settle 
and pour off the clear supernatant liquid, which should be a dilute 
solution of hydrogen peroxide. 


BaO, + H,SO, = H,O, + BaSQ,. 
2. Tests. Add some of it to a solution of potassium iodide—iodine 
is liberated, and turns the solution yellow. Collect it by shaking up 


with two or three drops of chloroform—a violet solution in the latter 
liquid is obtained. 


HYDROGEN PEROXIDE 135 


Add some to a dilute solution of potassium permanganate—the 
latter is decolorized. 

Dip a piece of filter paper into a solution of lead acetate, expose it 
to sulphuretted hydrogen gas until it is converted into black lead 
sulphide, dry it and then place in a solution of hydrogen peroxide. 
The sulphide will be oxidized to white lead sulphate. 

3. Hstimation of Amount in Solution by titrating against Potassium 
Permanganate. Take 10 c.c. of a solution of hydrogen peroxide in 
a flask, add excess of dilute sulphuric acid, and run in from a 
glass-stoppered burette a standard solution of permanganate, till a 
pink colour is just permanent. 

A suitable strength of permanganate is one known as N/10, i.e. 
a solution containing 3-163 grams per litre. 

From an examination of the equation representing the reaction as 
given on the previous page, it will be seen that 316-3 grams react with 
170-1 grams of hydrogen peroxide to form 160 grams of oxygen. 

Now N/10 permanganate contains -003163 grams of K,Mn,O, per 
c.c., and suppose the volume required = v c.c., 

Then amount of H,O, in 1 c.c. of original solution = 

170-1 -003163 x v 
3163 10 

Perform the experiment three times and find the average. A 
10-volume solution should contain about -03 grams per c.c. 

4, Hstimation by collecting the Oxygen evolved when mixed with 
acidified Permanganate. Use the apparatus shown in Fig. 188. Fisa 
4 oz. flask into which is put a measured volume of hydrogen peroxide 
solution, say 10 c.c., and an equal quantity of dilute sulphuric acid. 

G is a burette which contains a fairly strong solution of potassium 
permanganate, and which can be run into F as desired, by means of a 
glass tap. 

E is a tube leading from F to a gas-collecting apparatus B made 
out of an inverted 100 c.c. burette. D is a swivel made from the neck 
of a broken Wurtz flask, in which works the gauge tube C. 

To experiment :—- 4 

Put peroxide solution and acid into F, and permanganate into G, 
taking care that the teat of the burette is filled. 

Fill B with water and fit up as shown in diagram. Open tap T to 
adjust pressure, and read the level of water at A. 

Run in permanganate from G until the solution in F is permanently 
pink. Readjust gauge tube C so that the top is level with the water 
surface in B. | 

Determine, by reading the new level, the volume of water expelled 
from B, subtract volume of liquid run in from G. 


= 0001701 X v grams. 


136 3 TEXTILE CHEMISTRY 


This gives volume of oxygen obtainable by using 10 c.c. of hydrogen 
peroxide ; calculate for 1 c.c. . 


O 
Ozone. QO, or 0,0 or | »o is a gas found in small quantities in 
O 


the atmosphere in certain districts. Its formation is said to be due to 
electrical action. Ozone is easily produced from oxygen or air, the 
process being termed ozonization, e.g. :— 

1. An electrical machine working in air yields an amount that is 
easily recognized by the sense of smell. 


2. If air be passed slowly over freshly scraped and moist yellow 
phosphorus, and the gas tested as it issues, it will be found to be 
ozonized (Fig. 189). 

3. Oxygen is passed through a glass vessel the outside and inside 
of which are respectively connected to the terminals of an induction 
coil. Fig. 190 shows Ostwald’s form, in which connexion is made to 
the coil by platinum wires dipping into dilute sulphuric acid. Copper 
wires will also serve the purpose if cleaned after previous use. 

Fig. 191 shows a Siemen’s ozone tube, and Fig. 192 a simple 
modification of the same. 

Ozone is also produced :— 

1. When dilute sulphuric acid is electrolysed, especially if the ~ 
current be strong and the electrodes made of thin platinum wire. 

2. When a red-hot platinum spiral is suspended in ether vapour. 

3. When manganese dioxide, or potassium permanganate, or 


OZONE 137 


barium peroxide is acted upon by sulphuric acid to produce oxygen, 
ozone is always liberated. 


PROPERTIES 

The chemical properties of ozone are very characteristic, although 
in some cases they are very analogous to those of hydrogen peroxide. 

It has a penetrating and rather unpleasant odour somewhat 
resembling chlorine ; when heated it is decomposed into oxygen; it 
is slightly soluble in water (0-45 per cent. by volume), condenses to a 
liquid at — 181° C., and in that condition it is highly explosive. It 
has powerful oxidizing and bleaching properties due to the ease with 
which it decomposes to liberate oxygen in an atomic condition. 


~ Tago - 


infotL 


) 


FIG.190 


LABORATORY EXERCISES WITH OZONE 


1. Investigate its action on a solution of potassium iodide. 

2. What happens when “starch iodide” paper is brought into | 
contact with it ? 

3. Perform the Houzeau test. Take a piece of litmus paper which 
has been made faintly acid with very dilute nitric acid, and dip it into 
a solution of potassium iodide. Expose it to ozone. It is immediately 
turned blue. 


Reaction: 2KI + O, + H,O = 2KOH + I, + O,. 


The caustic potash (KOH) is alkaline, and this turns the red litmus 
blue. 

4. Pass ozonized oxygen through a piece of rubber tubing. The 
gas which emerges has lost its ozone. Why ? 

5. Pass some through a heated glass tube. What happens ? 


a TEXTILE CHEMISTRY 


6. Shake some up with a globule of mercury and note that “ tails ” 
are produced. Can you explain this ? 

Estimation of the Percentage of Ozone in a Sample of ozonized Oxygen. 

Brodie’s method: The apparatus used is a special form of pipette 
shown in Fig. 193. 

Its capacity between m and m’ is known. It is first filled with 
strong sulphuric acid by opening tap a, and closing tap 0, and the 
pipette put in a vessel containing water at a definite temperature. 
The end near @ is connected to the supply of ozonized gas and 
sufficient drawn in to fill the pipette to the mark m. Tap a is closed, 
a vessel containing a solution of potassium iodide is placed under the 


Fig.193 


other end of the pipette, and tap b opened. The gas from m’ to m is 
now forced through the iodide solution, and finally the iodine liberated 
by this volume estimated. 

A simpler and equally efficient apparatus is shown in Fig. 194, 
which is made by bending the stem of a pipette. 

Ozonized oxygen may be made in it (A), or passed into it. To 
estimate the ozone, it should be inverted in a wide test tube containing 
strong sulphuric acid, and whilst it is slowly depressed in this liquid, 
the other end should be immersed in a solution of potassium iodide. 
When the strong sulphuric acid reaches the graduation mark the 
volume of gas denoted by the capacity of the pipette has been bubbled 
through the iodide solution. The free iodine is then estimated by 
means of a standard solution of sodium thiosulphate. 


SECTION XII 


ALUMINIUM 


T has been estimated that this element forms one-eighth of the 
| earth’s crust, but although so plentiful only one or two of its 

compounds can, up to the present, be successfully worked for 
the metal—and these are by no means the most plentiful. 

The metal is now prepared entirely by electrolysis. The electrolyte 
is a fused mass of cryolite, fluorspar, and alumina. Fig. 195 represents 
in principle the construction of the cell, the temperature of which is 
nearly 900°C. The oxygen which is liberated combines with the 


carbon of the electrodes to form carbon monoxide, the metal sinking 
to the bottom of the chamber, from which it is periodically tapped. 

The alumina, Al,O3;, is the portion of the electrolytic liquid which 
is decomposed, the fluorspar and cryolite acting as the flux and solvent. 

The annual production of aluminium has increased enormously 
during the last twenty or twenty-five years, and the price has rapidly 
fallen. Whereas in 1855 the commercial quality cost £3 10s. per oz. 
and was a chemical curiosity, it is now (normally) 6d. a lb. 


139 


140 TEXTILE CHEMISTRY 


PROPERTIES 


It is a “tin white’ metal of great tensile strength, very ductile 
and malleable, extremely sonorous, and has a low sp. gr. (2-6); _ its 
melting-point is 625° C. 

It does not tarnish in ordinary air at ordinary temperatures, but 
burns when strongly heated to form a white oxide called alumina 
(Al,0,;). Nitric acid has not much action on it, but it is dissolved 
by hydrochloric to form the trichloride. 

Aluminium is much more readily attacked by alkalis, particularly 
caustic soda, potash, and washing soda. A solution of common salt 
will act upon it, and so will organic acids in the presence of this com- 
pound—consequently alkaline liquids must not be boiled in aluminium 
vessels. 

It is a powerful reducing agent, and is used in the “ Thermit ” 
process in the powdered condition for reducing oxides of iron, man- 
ganese, chromium, etc., to the metallic condition in small welding 
operations. 

Several important alloys are made from it, of which the best known 
are aluminium bronze (90 per cent. copper, 10 per cent. aluminium) 
and magnalium (90 per cent. aluminium, 10 per cent. magnesium, 
etc.). | 

Uses. For metallic parts of airships, aeroplanes, balances, cooking 
utensils, surgical instruments, paint, reducing agent, ornamental and 
decorative purposes. 

In some ways its use is restricted by the difficulty experienced in 
soldering it—no really satisfactory method of doing this has been 
invented yet. 


Chief Compounds of Aluminium. 

1. The Alums. These are double sulphates; the potassium salt 
was one of the earliest compounds of the metal prepared. Al,(SO,);. 
K,S0O,.24H,0. 

2. Clay. Kaolin, or China clay, contains a large percentage of © 
the metal. Its composition is Al,O3;.2Si0,.24H.0. Clay of all kinds 
consists essentially of silica and alumina in varying proportions, 
associated with smaller quantities of lime, magnesia, oxides of iron, 
and alkali metals. 

3. Cryolite. 3NaF.AIF;. Largely used as a flux in certain metal- 
lurgical operations. 

4. Aluminium oxide, Al,O,—alumina. In a natural condition it 
occurs associated with small quantities of other metallic oxides as 
bauxite, corundum, emery, ruby, amethyst, sapphire, topaz, turquoise. 

5. Aluminium trichloride, Al,Cl,, used for carbonizing cotton in 
mixtures of cotton and wool, is prepared in the anhydrous condition 


ALUMINIUM, ZINC, MAGNESIUM 141 


by passing chlorine gas over heated aluminium foil, and for ordinary 
purposes by the action of strong hydrochloric acid on the metal and 
concentrating the solution. 

6. Other salts used for textile purposes are the acetate, made by 
dissolving the hydroxide in acetic acid, or by the addition of lead or 
‘ calcium acetate solution to a solution of aluminium sulphate. The 
impure commercial acetates of aluminium are used by dyers and 
calico-printers as mordants for alizarine reds, and on that account 
are known in trade as “ red liquor.” 

Aluminium acetate is a very efficient “ shower-proofing ”’ chemical 
for cotton or wool cloth. The material to be treated is put for some 
hours in a warm solution of the salt (strength 8°-10° Twaddell), then 
passed through a soap solution containing 50-75 grams of soap per 
litre at a temperature of about 45°C., dried in a hot chamber and 
calendered. Japan wax, gums, oils, paraffin, wax, etc., are sometimes 
added to the soap bath. 

Preparation of Alum. 

1. In the laboratory, by adding aluminium sulphate to potassium 
sulphate in proper proportions and crystallizing from the hot solution. 

2. From alum stone—Al,(SO,)3;.K,S0,.2Al,0;.8H,O. The material 
is calcined and then the liquid lixiviated with hot water when the 
Al,O; remains undissolved. The alum may be crystallized out after 
sedimentation. Or, the calcined mass is treated with sulphuric acid 
to dissolve the oxide and then before crystallization the requisite 
amount of potassium sulphate is added. 

The former method produces what is called Roman alum. The 
iron present as an impurity may be separated by filtration and 
recrystallization. 

3. From alum shale, which is a rocky mass consisting of aluminium 
silicate and iron pyrites. It is first roasted and exposed to air and 
moisture. The pyrites is oxidized and sulphuric acid is formed, 
which acts upon the shale, making aluminium sulphate. The mass is 
lixiviated, concentrated, and potassium chloride added. The iron 
sulphate which has also been formed is decomposed to chloride, and 
potassium sulphate produced. When concentrated it is well stirred 
to ensure the precipitation of the alum in small crystals—the product 
being known as “ meal.” 

4. From bauxite (Al,0;). This mineral is roasted, treated with 
sulphuric acid, and lixiviated with water. The solution is concentrated, 
potassium chloride added and then crystallized. 

5. From clay. Purified and calcined China clay is boiled with 
oil of vitriol for several hours, then with several times its weight of 
water till it makes a syrup. It is filtered and cooled, the correct 
amount of potassium sulphate added and then crystallized. 


142 TEXTILE CHEMISTRY 


Alum is very soluble in hot water, but only slightly in cold :— 


100 grams of water at 0°C. dissolve 3-9 of alum. 
93 399 be) 50° C. Bs 44-1] \ 99 
” 99 re) 100° C. 9 357-5 » 


It is insoluble in alcohol; when heated it melts and dissolves in 
its own water of crystallization, which is gradually expelled, until at a 
dull red heat a non-crystalline and anhydrous substance is obtained 
called burnt alum, which is much less soluble in water than the 
crystalline form. 

The chief use for alum is as a mordant in dyeing. When sodium 
carbonate or sodium hydrate is added to alum solution, till the pre- 
cipitate first formed is redissolved, a basic alum (called neutral alum) 
is formed. This compound very readily gives up alumina to fibres 
impregnated with it. If the fibres coated with this mordant be now 
passed through solutions of certain colouring matters, the two unite 
to form a coloured “lake ’’ which is not removed by boiling water. - 

Aluminium sulphate, also known as cake alum, patent alum, 
concentrated alum, and in the impure condition containing considerable 
quantities of iron, as alumino-ferric, is prepared by dissolving alu- 
minium hydroxide, bauxite, or clay in sulphuric acid. It has an acid 
reaction and is used instead of alum for many purposes. 

Aluminium hydroxide is formed as a white gelatinous precipi- 
tate when caustic alkalis are added to solutions of aluminium salts. 
It has considerable application as a precipitating and clarifying agent. 


ZINC 


Zinc, its alloys and compounds, are of great practical importance. 
The metal itself is used in large quantities for coating sheet iron 
(so-called galvanized iron), and in the powdered condition as a reducing 
agent for indigo. 

Brass, bronze, and German silver—in all of which zinc is present— 
have a very wide application. Zinc oxide is used as a pigment, and 
zinc chloride is the most generally used antiseptic in the cotton 
industry. Other important compounds are white vitriol, or zinc 
sulphate, zinc carbonate, and zinc sulphide. 

The ores used for the extraction of the metal are :— 

1. Calamine or zinc carbonate. 

2. Blende, black jack or zine sulphide. (‘The colour of this ore is 
due to the presence of sulphide of iron as an impurity.) 

3. Red zinc ore—an impure oxide. _ 

Extraction. The ore is first calcined to convert it into the oxide, 
and then it is mixed with carbon and strongly heated in retorts, when 
the oxide is reduced first to the metallic condition and then vaporized. 
The gaseous metal is condensed in receivers. | 


ALUMINIUM, ZINC, MAGNESIUM 143 


In the Belgian process the retorts are small, being about 3-4 ft. 
long and 9 in. in diameter, as many as 80 being put in one furnace, 
each holding a charge of about 40 lb. 

The Silesian furnace contains about 30 retorts, @ shaped in section, 
and are much larger than those used in Belgium, each holding a 
charge of 5 cwt. 

The condensing-chambers are attached to the mouths of the retorts 
as shown in Fig. 196. 

The metal so obtained is called “ spelter’’ and is very impure— 
lead, iron, tin, antimony, arsenic, copper, cadmium, magnesium, and 
aluminium may all be present. 

It may be purified by redistillation, but a better product is obtained 
if it is dissolved in acid, the carbonate produced by precipitation, 
and this compound reduced with charcoal made from sugar. 

Zinc is very malleable at a temperature of 121° C., but when heated 
to 204° C. it again becomes brittle and can be powdered up in a mortar. 

When exposed to air it is 
slowly attacked to form zinc 
oxide, which gradually changes 
to the carbonate; and this 
layer when completely formed 
over the surface protects it 
from further oxidation. 

The metal is very soluble 
in dilute acids, alkalis, and 
slightly in boiling water or 
steam. The salts of zinc so formed are very poisonous, and therefore 
zine vessels are not suitable for cooking utensils. Galvanized cisterns 
for storing water are on that account objectionable unless they be 
coated finally with a layer of tin. 

Zinc chloride is a very important textile chemical, and is made 
by dissolving all sorts of waste zinc, ashes and skimmings, in hydro- 
chloric acid. It can also be made by dissolving calamine in the same 
acid. 

Commercial zinc chloride is liable to contain several impurities, the 
methods for detecting which are given in Section XV, pages 188-189. 
The manufacturer endeavours to produce a product free from acid 
and iron. For use in this country it is usually sold as a strong solution 
in water—about 100°-104° Twaddell, but for export purposes it is 
further concentrated till it sets as a solid on cooling and contains 
up to 95 per cent. of anhydrous zinc chloride. 

The substance known in the cotton trade as “zinc,” or “ anti- 
septic’ is zinc chloride. Occasionally the term “anti” is used to 
denote magnesium chloride. | 


Idd TEXTILE CHEMISTRY 


By boiling a solution of zine chloride of sp. gr. 1:7 with excess of 
zinc oxide, a basic or oxychloride is obtained which dissolves silk and 
is used to estimate that material when mixed with wool and vegetable 
fibres. 

Zinc chloride is very hygroscopic, and a very efficient “‘ fungicide ” 
for cotton. It is very soluble in water, slightly in alcohol; has a 
melting-point of 250°C., and a boiling-point of 730°C., but while 
being heated to that temperature, particularly if water be present, 
considerable decomposition results, hydrochloric acid being evolved 
with reduction to oxychloride. 

Zinc sulphate, known in the crystalline condition as “ white 
vitriol,” ZnSO,.7H,O, can be made by dissolving the metal in dilute 
sulphuric acid, or roasting the ores and then treating them with the 
acid and recrystallizing. 

It has some application in dyeing and caliadroanennen ; it is used 
in the tanning industry as a preserving and clarifying agent, as an 
astringent in eye “ lotions,” and as a dryer for boiled oil when used 
in paint. 

Zinc oxide and zinc sulphide are both used as pigments. The 
former can be prepared by burning the metal in air, and the latter 
by precipitating from solutions of the chloride or sulphate with sul- 
phuretted hydrogen in alkaline solution, or heating an intimate 
mixture of zinc dust with half its weight of powdered sulphur. 

Compounds of zinc heated on charcoal in an oxidizing flame give 
a white infusible residue. If this be allowed to cool and a few drops 
of cobalt nitrate solution dropped on it and the mass again heated, 
a very distinctive green residue is formed. 


MAGNESIUM AND ITS CHIEF COMPOUNDS 


The element itself does not occur free in nature, but it is present 
in several minerals, the most important being :— 

1. Magnesite or magnesium carbonate, MgCOQ3. 

2. Dolomite or magnesium limestone—mixed carbonates of 
magnesium and calcium. 

3. Kieserite—magnesium sulphate, MgSO,.H,0. 

4, Carnallite—magnesium and potassium chlorides :— 

MgCl.KC16H,.O. 

5. Epsom salts—magnesium sulphate, MgSO,.7H,O. 

6. Various silicates, e.g., talc, horneblende, asbestos, olivine, 
meerschaum, serpentine. . 

The metal is prepared by the electrolysis of the fused chloride. A 
temperature of 700°C. is obtained by surrounding an iron crucible 
with burning “ gaseous fuel.” ‘The crucible is the cathode. The 


ALUMINIUM, ZINC, MAGNESIUM 145 


anode is a stout carbon rod, surrounding which is a porous cylinder to 
convey away the liberated chlorine. 


PROPERTIES OF THE METAL 
Sp. gr. 1:75; melting-point, 632°C.; boiling-point, 1,100° C. 
It is a silver-white metal, ductile at high temperatures and fairly 
malleable. It oxidizes slowly in moist air, but not in dry air or 
oxygen. Heated in air, it burns, giving a dazzling white flame rich 
in chemical rays. On this account it is used as an artificial illuminant 
in photography, but, owing to the production of a white smoke of 
magnesium oxide, it cannot be used long at a time. Burning mag- 
nesium is often employed to examine and compare dyed fabrics for 
shade. 
Heated in steam, it decomposes it, forming the oxide and liberating 
hydrogen. Lighted, and plunged into carbon dioxide, it continues 
to burn, decomposing the gas with liberation of carbon and formation 
of magnesium oxide. Heated in nitrogen, it combines with it to form 
a nitride, Mg,N,. This was one of the earlier methods adopted for 
the isolation of argon from the atmosphere. 
It is very soluble in dilute acids and solutions of ammonium salts, 
with liberation of hydrogen, this occurring even with nitric acid if 
it be sufficiently dilute and a few inches of magnesium ribbon used. 
It is insoluble in caustic potash or ee It is a powerful reducing 
agent at high temperatures. 
‘The chief compounds of magnesium are the chloride, oxide, 
sulphate, and carbonates. 
Magnesium chloride (MgCl.) can be prepared :— 
1. From the natural carnallite by fractional crystallization. Mag- 
nesium chloride is much more soluble than potassium chloride, and 
thus remains in the mother liquor after most of the latter has been 
deposited. The crystals when formed by further concentration have 
the composition MgCl,.6H,O, and are very deliquescent. 
2. By burning the metal in chlorine :— 
Mg + Cl, = Mg(l,. 

3. By dissolving the metal in hydrochloric acid :— 
Mg + 2HCl = MgCl, + H,. 

4. By dissolving the oxide in hydrochloric acid :— 
MgO + 2HCl = MgCl, + H,.O. 

5. By dissolving the carbonate in hydrochloric acid :— 
MgCO, + 2HCl = MgCl, + H,O + COQ,. 

To obtain the anhydrous salt, concentration of the solution to 
dryness will not suffice, as it undergoes a series of chemical changes 
which are represented finally by the equation :— 

MgCl,.6H,0 = MgO + 2HCl + 5H,0. 
10 


146 TEXTILE CHEMISTRY 


Although the anhydrous chloride is never required for textile 
purposes, this reaction is very important because it explains what 
happens in “singeing’’ when a cloth contains magnesium chloride. 
In this case it is the liberated hydrochloric acid which, acting on the 
cotton, converts it into hydrocellulose and so produces tendering of 
the fabric. 

If ammonium chloride be added to a solution of magnesium 
chloride, a double salt is formed, MgCl,.NH,Cl.6H,O. When this is 
heated it is first dehydrated, and then the ammonium chloride vola- 
tilizes, leaving the anhydrous magnesium chloride as a fused mass, 
which congeals to a white crystalline solid. 

Magnesium chloride is a very deliquescent substance, and on this 
account it is largely used as a sizing ingredient, particularly in the 
“heavy trade.” Its use is attended with considerable danger unless 
zine chloride or some equally efficient antiseptic be used with it, as 
it has no antiseptic properties whatsoever. The substance is often known 
under the name of “ anti’—a most unfortunate term, as it tends to 
convey the impression that it has preservative properties. | 

Magnesium oxide or magnesia (MgO) is obtained by :— 


1. Burning magnesium in air or oxygen. 
2. Calcining magnesium nitrate (MgNO;), = MgO + 2NO, + O. 
3. Calcining the carbonate or basic carbonate :— 
MgCO; = MgO + CO,. 
4. Converting the chloride into carbonate, and then gently igniting 
the dried powder. If excess of sodium carbonate is added and the 


mixture well boiled, the composition of the carbonate produced is 
2MgCO;.Mg(OH)..2H,O. On ignition this becomes 


3MgO + 2CO, +3H,0. 


The hydroxide is obtained by dissolving the oxide in water. 
Solubility of the oxide is about 1 in 55,000 of cold water, and Jess in hot. 

Magnesium sulphate (MgSO,) occurs naturally in the Stassfurt 
deposits as kieserite, MgSO,.H,O. Upon treating this with water 
and recrystallizing, the pure salt is obtained as MgSO,.7H,0. It is 
present in many mineral springs, and from its occurrence in one of 
them has been named Epsom salts. 

When the carbonate is treated with dilute sulphuric acid, the 
following reaction occurs :— 


Mg0O, + H.SO, = MgSO, + H,O + CO,. 
If magnesium limestone is used, sulphates of lime and magnesia 
are both formed. The former, being insoluble, may be removed by 


sedimentation, but obtained in this way the magnesium sulphate is 
not so pure as that made from kieserite. 


SULPHUR 147 


The salt has a bitter taste ; it is completely dehydrated at 200° C. ; 
its solubility at ordinary temperature is 126 in 100 of water. It has a 
considerable application in medicinal saline mixtures, and in textiles 
it is used as a finishing material in certain kinds of finishes for cotton 
cloth. For this purpose it is advisable that it should be free from traces 
of magnesium chloride, as the presence of the latter may lead to partial 
solution of the sulphate when the cloth is in a humid atmosphere. 
When the cloth becomes drier, the sulphate recrystallizes in the fibre, 
which results in tendering of the fabric, particularly if it be repeated 
once or twice. 

Magnesium carbonate, MgCO;, occurs naturally as magnesite, and 
as magnesium limestone mixed with calcium carbonate. 

It is decomposed by heat much more easily than calcium carbonate 
to form the oxide with liberation of carbon dioxide. 


SULPHUR 


This is an element which occurs in large quantities in nature, both 
in the free state and in combination. 

1. As native sulphur (i.e. sulphur uncombined, but mixed with 
earthy matter) in all volcanic districts, e.g. Italy, Sicily, Iceland, 
United States. 

2. Forming sulphides with certain metals, it occurs in most ores, 
e.g. pyrites or iron sulphide, copper pyrites, galena or lead sulphide, 
zine blende, cinnabar or mercury sulphide, etc. 

3. Sulphates which contain sulphur combined with a metal and 
oxygen, e.g. gypsum, alabaster or calcium sulphate, heavy spar or 
barium sulphate, kieserite or magnesium sulphate, etc. 

Sulphur is prepared chiefly from native sulphur, but considerable 
quantities are also obtained from alkali waste and coal-gas waste. 

1. From native sulphur. It is liquated where found, i.e. it is stacked 
on the side of a slope, covered with a turf roof and fired, the entrance 
of air being reduced to a minimum. Some is burnt, which supplies 
the heat to melt the rest, which then flows along the sloping floor until 
it gets outside the stack (Fig. 197). This simple process separates it 
from a considerable quantity of the earthy matter with which it was 
mixed. In this condition it is generally shipped. It is afterwards 
purified by redistillation (Fig. 198). 

2. From alkali waste (Mond’s process). Alkali waste is a mixture 
of calcium sulphide and. calcium oxide. It is suspended in water and 
oxidized by blowing a current of air through it. This produces such 
compounds as calcium thiosulphate, calcium polysulphides, calcium 
hyposulphide, etc., and liberates a large quantity of sulphur. It is 
alternately oxidized and lixiviated, and finally hydrochloric acid is 


148 TEXTILE CHEMISTRY 


added to precipitate the remainder of the sulphur, which is purified 
as before by distillation. 

3. From coal-gas waste, which is hydrated ferric oxide which has 
absorbed the sulphuretted hydrogen from coal gas. It is exposed to 
air and moisture, by which means sulphur is liberated. The mass is 
afterwards distilled. 


4. By mixing sulphur dioxide and sulphuretted hydrogen gases in 
the presence of water vapour sulphur is precipitated. 

Sulphur can be prepared in at least four distinct varieties or 
allotropic modifications. 

1. Rhombic sulphur, made by dissolving sulphur in carbon di- 
sulphide, filtering and allowing the clear liquid to evaporate slowly at 

ordinary temperature. : 

2. Prismatic sulphur, prepared by care- 
fully melting sulphur in a beaker, allowing 
it to stand until it has partly solidified, and 
then pouring away the still liquid portion. 
Prismatic crystals line the sides and bottom 
of the beaker. 

3. Plastic sulphur is formed when melted 

sulphur is poured in a thin stream into cold 
Fig. 199 water (Fig. 199). 

4. White amorphous sulphur is produced when carbon disulphide 
is exposed to sunlight, or when hydrochloric acid is added to ammonium 
sulphide. It is insoluble in carbon disulphide. 


PROPERTIES OF THE RHOMBIC AND STABLE VARIETY 
Insoluble in water; soluble in carbon disulphide; burns with 
a pale blue flame to form sulphur dioxide; non-conductor of 


SULPHUR 149 


electricity ; bad conductor of heat; yellow in colour; melts at 
114°C. to a pale yellow liquid, which is very mobile. Heated still 
further, the liquid gradually darkens in colour and becomes more 
and more viscous, until at 230° C. it is almost black and can scarcely 
be poured from the vessel; heated to a higher temperature, it 
becomes somewhat less viscid but still remains black, and ultimately 


a 


f1g.200 


To Use.—Put in the acid and iron sul- 
phide. Open the tap—the acid acts on 
the sulphide and liberates the gas, which 
passes through the solution. When enough 
has passed, close the tap; the gas then 
collects and forces the acid back into its 
own tube, thus stopping the action. The 
acid and sulphide tubes are connected by 
india-rubber tubing. 


boils at 448°C. In cooling it goes through similar changes in the 
reverse order. 

Sulphur is used largely in the manufacture of sulphuric acid, 
ebonite, vulcanite, matches, gunpowder, dye-stuffs, sulphides, etc., 
and also as a fungicide and insecticide. 

Hydrogen sulphide, or, as it is commonly termed, sulphuretted 
hydrogen, is by far the more important of the two compounds which 
sulphur forms with hydrogen. It is found dissolved in certain natural 
mineral waters, e.g. at Harrogate, and it is evolved from active 
volcanoes. 


150 TEXTILE CHEMISTRY 


Preparation :— / 

1. If the pure gas be required, antimony trisulphide is treated with 
strong hydrochloric acid. | | 

2. For ordinary purposes ferrous sulphide (made by melting 
powdered sulphur with iron filings until combination results) is acted 
upon with dilute sulphuric acid or moderately strong hydrochloric acid 
in one or other of the forms of apparatus shown in Figs. 200-203. 

The correct method of using each form is given under its own 
illustration. ; 

In Fig. 201 the iron sulphide is placed in the vessel A, and water 
in the wash bottle D. Hydrochloric Acid (1 : 1) is poured through the 


fic.202 


Acid is put in the top bulb, 
from which it passes to the 


bottom and then to the centre. When in use the aspirator containing the acid should 
As soon as it reaches the sul- be placed on a block of wood. 

phide the tap should be closed. After using the gas the tap should be closed, then the 
As the gas accumulates the acid aspirator containing the acid put on the bench and the 
is forced back. one containing the sulphide put in its place. 


funnel E and into the reservoir F until the bottle G is filled, and the 
acid begins to fall on the sulphide in A. The evolved gas passes up 
through the water in D, and is drawn off at the tap H, which is placed 
outside the cabinet, away from the working parts of the apparatus. 
When the tap is closed the acid is driven into the bottle G, and thence 
to the reservoir F. Communication between G and A can be stopped 
by the clip I. 

Used acid is withdrawn from A into the basin B by removing 
the glass rod C. ; 

3. It may also be prepared from its elements by direct union, by 
passing a stream of hydrogen and sulphur vapour through a strongly 
heated tube. 


HYDROGEN SULPHIDE 151 


4. The gas is also produced when organic matter containing sulphur 
decays, e.g. eggs. When coal is distilled, sulphuretted hydrogen is 
evolved, and on that account the coal gas is “scrubbed ” before it 
reaches the gasometer. 


PROPERTIES 


Colourless gas; extremely foetid smell and very poisonous if 
breathed into the lungs. It is on this account that the gas is generated 
in special forms of apparatus, which should be kept (and used) in a 
fume chamber if possible. 

It is soluble in water to the extent of about 3 in 1 at ordinary 
temperatures. Its solution is acid to litmus, and decomposes after a 
time on exposure to air—sulphur being precipitated. 

The gas burns with a bright blue flame, producing sulphur dioxide 
and water. It forms an explosive mixture with oxygen when mixed 
in the proportion of 2 to 3. 

When passed into strong sulphuric acid it is decomposed—sulphur 
dioxide, water, and sulphur being formed. It is absorbed by lime, but 
calcium chloride has no action on it. 

In contact with metals, or when passed into metallic solutions, it 
produces sulphides, e.g. tin, lead, silver, etc. The “lead reaction ”’ is 
used as a test for the gas. 

The chief use for hydrogen sulphide is as a laboratory reagent. Its 
reactions in this respect form the basis of the ordinary methods of 
analytical chemistry. 

It is also used—generally in the form of ammonium sulphide—for 
“ oxidizing ”’ (sic) copper and silver in art metal work. 

Preparation of Hydrogen Sulphide—experiments illustrating its Proper- 
ties. Its action on metallic Solutions in the Formation of Sulphides. 

Arrange the apparatus shown in Fig. 200. 

Place ferrous sulphide in left-hand vessel and hydrochloric acid 
—half strong, half water—in the other. 

Open the clip; the acid flows amongst the iron sulphide and 
evolves sulphuretted hydrogen. 

Tests. 1. Is it soluble in water ? 
2. Describe its smell. 
3. Does it burn? Does it support combustion ? 
4. Action on lead acetate paper. 

Note its action on “ metallic solutions.” © 

Pass a stream of sulphuretted hydrogen through each in turn. 

Note. 1. Whether a precipitate of a sulphide is produced, i.e. 

Is it soluble or insoluble in water ? 
2. The colour of the precipitate (if there be one). 


152 TEXTILE CHEMISTRY 


Test :— 

Filter  off,\ 3. Its solubility in hydrochloric acid. 
wash, and divide 4. a », ammonia. 
the precipitate 5. ts », nitric acid. 
into five parts in 6 7 ,, ammonia disulphide. 
separate T.T.’s. a yf », ammonium chloride. 


Carefully record all your results. 

Note what a large number of metallic solutions yield sulphides when 
treated with hydrogen sulphide, and the great similarities when treated 
with certain reagents. There are also many points of difference when 
individually considered, especially in regard to colour. 

It is on this account that the reactions of the sulphides of the metals 
are most often used as the basis of analytical chemistry. 


SoME OF THE PRINCIPLES OF ANALYSIS 


I. Sulphides which are insoluble in hydrochloric acid—that is, if a 
solution of any of these metals be first acidulated with hydrochloric 
acid and then the gas passed through: these sulphides will be pre- 
cipitated :— 

Mercury (ous, ic) silver, lead (partly), copper, cadmium, bismuth, 
tin (ous and ic), antimony, and arsenic (often called the copper group). 
All the rest of the sulphides are soluble either in hydrochloric acid or 
water. 

II. Sulphides which are soluble in hydrochloric but insoluble in 
ammonium hydrate :— 

Iron (ous and ic), chromium, aluminium, nickel, cobalt, zinc, 
manganese, magnesium. (Iron and zinc group.) 

III. Sulphides which are soluble in acid, alkali, and water :-— 

Barium, strontium, calcium, potassium, sodium, ammonium. 

IV. Silver, mercury (ous), and lead (partly) are precipitated as 
chlorides when the hydrochloric acid is added to the solution. (Silver 
group.) 

It is also possible to subdivide the groups. Thus— 

In the copper group : arsenic, antimony, and tin sulphides are all 
soluble in ammonium disulphide. (Arsenic sub-group.) 

In the iron and zinc group : The hydrates of iron, chromium, and 
aluminium are insoluble in water. Therefore when ammonium hydrate 
is added to solutions of salts of these metals, a precipitate is produced 
before sulphuretted hydrogen is passed. 

Again, magnesium sulphide is not precipitated in the presence of 
ammonium chloride. Its phosphate is insoluble in water. 

In Group III a division may be made by precipitating barium, 
strontium, and calcium as carbonates—which are all insoluble in water. 
(Barium group.) | 

These operations are generally referred to as Grouping. 


QUALITATIVE ANALYSIS 153 


The order of working will therefore be as follows :— 

1. Prepare a solution of the salt in water. 

2. Add enough hydrochloric acid to make the solution acid to 
litmus paper. 

A preciptiation indicates presence of silver group. (Silver, mercury 
(ous), lead.) 

No precipitation indicates the absence of silver group. 

3. Filter off the precipitate (if there be one). 

4. Pass through the solution (or filtrate) sulphuretted hydrogen gas. 

A precipitation indicates presence of copper group. Filter off and 
test its solubility in ammonium disulphide. 

If insoluble—absence of arsenic sub-group. 

If soluble—it is arsenic, tin, or antimony. 

Insoluble in ammonium disulphide, and is :— 

(a) Black—mercury (ic), lead, or copper. 

(6) Brown—bismuth. 

(c) Yellow—cadmium. 

No precipitation with sulphuretted hydrogen—shows absence of 

copper group. 
| 5. Boil the solution (or filtrate) for a few minutes, add a few drops 
of nitric acid, and boil again. (This is to get rid of the hydrogen sulphide 
and oxidize the iron.) 

6. Add ammonium chloride and then ammonium hydrate. 

A wprecipitation—presence of iron sub-group (iron, chromium, 
aluminium). 

No precipitation—absence of iron sub-group. 

7. Filter off the precipitate (if there be one). 

8. Pass through the solution (or filtrate) sulphuretted hydrogen. 

A precipitation indicates presence of zinc sub-group. 

(a) Zinc—white precipitate. 

(b) Manganese—flesh-coloured precipitate. 

(c) Nickel and cobalt—black precipitate. 

No precipitation—absence of zinc sub-group. 

9. Filter off precipitate (if there be one). 

10. Add to solution (or filtrate) ammonium carbonate. 

A precipitation—barium, strontium, or calcium carbonates. 

No precipitation—absence of barium group. 

11. To filtrate or solution add sodium phosphate, when mag- 
nesium phosphate will be precipitated if a magnesium salt were 
present. 

12. Potassium, sodium, and ammonium are identified separately 
and by other means. 

In order that the student shall be able to apply simple tests to 
identify textile chemicals and mill stores it is very advisable that he 


154 TEXTILE CHEMISTRY 


should have some knowledge of analytical processes, and a suitable 
exercise at this stage is the analysis of a simple salt. 


SCHEME FOR THE ANALYSIS OF A SIMPLE SALT 


Preliminary Tests. 

1. Heat the substance alone in a small dry test tube. 

Odour of sulphur dioxide—hydrosulphuric or sulphurous acid. 
Evolution of carbon dioxide—carbonic acid. 

Metallic sublimation—mercury. 

Yellow hot, white cold—zinc. 

2. Treat with dilute hydrochloric acid, and determine the nature 
of the gas or vapour evolved (see page 52). 

3. Treat with strong sulphuric acid. 

4, Treat with strong sulphuric acid and lead peroxide. 

5. Put a grain or two in a watch-glass, add strong hydrochloric 

acid ; dip into it a platinum wire, and find 
Colour the “flamereaction.” (For method of hold- 
ing the wire in the colourless bunsen flame, 
see Fig. 204.) 
“ Green—barium, copper, boric acid. 
Glass Yellow—sodium. 
handle Violet—potassium (red through indigo 
prism or cobalt glass). 
Red—calcium (lime). 
Crimson—strontium. 

6. Make a borax bead by fusing some 
borax on the end of a platinum wire. Fuse 
in a minute portion of the substance and note the colour of the bead. 

Blue—cobalt, copper. 
Violet—manganese. 
7. Fuse a little on charcoal in the reducing flame of a blowpipe. 
Beads or scales of metal—silver, copper, iron, cobalt, nickel, 
tin, lead, bismuth, and antimony. 

8. Fuse some more on charcoal in oxidizing flame. Cool, and then 
moisten the residue with a solution of cobalt nitrate. Reheat in the 
same flame— 

Blue residue—aluminium. 
Green residue—zinc. 
Pink residue—magnesium. 

9. Prepare a solution (a) in water, or if insoluble (b) nitric acid 
or (c) hydrochloric acid. (d) If not soluble in water or dilute acid, 
fuse with fusion mixture, and then boil the “melt” with water. 
Filter. In the filtrate examine for acids, and test the residue, 
after dissolving in hydrochloric acid, for bases. 


Tig, 20¢ 


QUALITATIVE ANALYSIS 155 


To detect the Basic Radicle :— 
1. To one portion of the solution add a solution of caustic soda. 

(a) White precipitate soluble in excess—lead, zinc, antimony, 
aluminium, tin. 

(6) White precipitate insoluble in excess—bismuth, cadmium, 
magnesium, calcium, barium, strontium, manganese 
(darkens). 

(c) Yellow precipitate—mercury (ic). 

- (d) Black precipitate—mercury (ous). 

(ec) Blue precipitate—copper, cobalt. 

(f) Dark brown precipitate—silver. 

(g) Dirty green precipitate—iron (ous). 

(h) Reddish brown precipitate—iron (ic). 

(7) Green soluble in excess—chromium. 

(7) Green insoluble in excess—nickel. 

(k) Evolution of ammonia gas—ammonium. 

(1) No precipitate—arsenic, potassium, sodium, ammonium. 

2. To another portion add hydrochloric acid. 

White precipitate—lead, mercury (ous), silver. Wash this 
precipitate with warm ammonia. 

No change—lead. 

Dissolves—silver. 

Blackens—mercury. 

3. If no precipitate has been produced with the acid, to the same 
_ solution add sulphuretted hydrogen gas. 
Black precipitate—mercury (ic), lead, copper. 
Dark brown precipitate—bismuth, tin (ous). 
Yellow precipitate—cadmium, arsenic, tin (ic). 
Brick red precipitate—antimony. 
4. If no precipitate in Nos. 1 and 2, to a fresh portion of solution 
add ammonium chloride and ammonia. 
Dirty green precipitate—iron (ous). 
Reddish brown precipitate—iron (ic). 
Green precipitate—chromium. 
White precipitate—aluminium. 
5. If no precipitate in No. 4, to the same solution add ammonium 
sulphide. 
Black precipitate—nickel, cobalt. 
White precipitate—zinc. 
Buff precipitate—manganese. 
6. If no precipitate in No. 5, to the same solution add ammonium 
carbonate solution. 
White precipitate—barium, strontium, calcium (distinguish 
by flame reactions). 


156 TEXTILE CHEMISTRY 


7. If no precipitate in No. 6, boil down the same solution, add more 
ammonia and then sodium phosphate. 

White crystalline precipitate—magnesium. 

To detect the Acidic Radicle :— 

Test solution with litmus. If acid, neutralize with ammonia (any 
precipitate may be filtered off and neglected) ; if alkaline, neutralize 
with nitric acid. 

1. To some of the neutral solution add silver nitrate. If a precipi- 
tate is produced, divide it into two parts. 

(a) Try the effect of heat on one part. 
(b) Determine if soluble or insoluble in nitric acid with the 
other part. 

If the precipitate be soluble in nitric acid and is :— 

(a) White, rapidly darkening—it may be thiosulphuric. 
(b) White, darkened by heat—it may be sulphurous, boric, 
carbonic. 
(c) White, dissolved on heating—it may be acetic. 
(d) White, unaltered by heat—it may be oxalic, tartaric, citric. 
(ec) Yellow—it may be phosphoric, arsenious. 
(f) Brown—it may be arsenic. 
(9) Red—it may be chromic. 
If the precipitate be insoluble in nitric acid and is :— 
(a) White, turns purple—it may be hydrochloric. 
(6) White—it may be hydrocyanic. 
(c) Yellowish white—it may be hydrobromic. 
(d) Yellow—it may be hydriodic. 
(ec) Black—it may be hydrosulphuric. 

Confirmatory tests with the original solution should be applied to 

distinguish :— 
Thiosulphuric—with hydrochloric acid gives a yellow precipitate 
and evolves sulphur dioxide. 
Sulphurous—with hydrochloric acid gives off sulphur dioxide. 
Carbonic—with hydrochloric acid evolves carbon dioxide. 
Boric—acidify with hydrochloric, dip in turmeric paper, dry it, 
the paper turns green. 
Acetic—warmed. with strong sulphuric acid—odour of vinegar. 
(a) Add calcium chloride solution. 
(1) White precipitate in the cold—oxalic, tartaric. 
(2) White precipitate on boiling—citric. 
(b) Heat another portion with strong sulphuric acid. 
(1) Blackens—tartaric. 
(2) No blackening—ozalic. 
Phosphoric—add a little of the original solution to ammonium 
molybdate solution warm—yellow precipitate. 


QUALITATIVE ANALYSIS 157 


Arsenic or Arsenious—put some of the original substance in an 
ignition tube with a small piece of charcoal and heat in bunsen 
flame—mirror of metallic arsenic sublimes. 

Chromic—Lead acetate gives a bright yellow precipitate. 


Hydrochloric Heated with chlorine evolved 
a peroxide | 
Hydrobromic and bromine evolved 
strong Bere) 
Hydriodic acid iodine evolved 


Hydrocyanic (Prussian blue test)—add solutions of ferrous sul- 
phate and ferric chloride, then excess of caustic soda. Boil, 
cool, and acidify with hydrochloric acid. 

Hydrosulphuric—add hydrochloric acid—sulphuretted hydrogen 
evolved. 

2. If silver nitrate does not give a precipitate in the neutral solution 
all the above-named acids are absent. 

Acidify a fresh portion of the solution with nitric acid, and add a 
solution of barium nitrate. 
. White precipitate = sulphuric acid. 

3. If still no precipitate, test the original substance as follows :— 

Dissolve in water (all nitrates are soluble in water). To this 
solution add a few c.c. of strong sulphuric acid, carefully cool the 
mixture, and when cold, pour on the top of it a strong cold solution of 
ferrous sulphate. A “ brown ring” at the junction indicates nitric 
acid. 


APPLICATION OF CHEMISTRY TO 
TEXTILES 


ALTHOUGH in its narrowest sense the term “textile” refers to the 
process of weaving only, by convention it has now a much wider 
significance, and is taken to include other branches of the manufacture 
of cotton, wool, and silk. 

In a similar sense we desire to use the term “ textile chemistry,” 
applying it with reference to instruction in the principles of all branches 
of the industry and particularly to the properties of the materials that 
are necessary to produce finished cloth from raw fibre. 

Textile chemistry in its more advanced form consists of a specialized 
study of each of the separate processes, and therefore the subject 
should be continued under the various branches, such as dyeing, sizing, 
bleaching, etc. 


SECTION XIII 
THE NATURAL FIBRES 


HE chief natural fibres in use in this country for textile pur- 
poses are cotton, wool, linen, and silk, of which the first 


two are by far the more important. 

Besides these a considerable amount of artificial silk is used. 

The characteristic appearance of fibres can be seen best under 
the microscope. The principle of the construction of this instrument 
is illustrated in Fig. 205. 

The object under examination is placed just beyond the focus (F) 
of a lens (called the objective) of short focal length. Rays of light 
passing through this lens produce on the other side an enlarged 
inverted image (first image). If a screen be placed in this position, the 
image will appear as a picture on it. If no screen be interposed, but 
another lens (eyepiece), of longer focal length, be placed between the 

158 


THE NATURAL FIBRES 159 


observer’s eye and this image, at a distance from the first image of a 
little less than its focal length, the rays from the image in passing 
through this latter lens are refracted in such a manner that an image 
of this image (second image) is produced, resulting in further 
magnification. 

Fig. 206 is a sketch of a Leitz microscope, and one that is very 
suitable for textile purposes. 

Before using a microscope the essential parts should be known, 
and a student using one for the first time should seek the aid of some 
person who has previously used one, as the instrument can be damaged 
very easily. 

The particular microscope illustrated consists of a brass stand with 
a substantial base—to the stand being attached, by means of a rack 
and pinion, a brass tube. Screwed to the bottom of this tube is a set 


of lenses called the objective; and fitting in the top is another set 
termed the eyepiece. The tube also can be made longer by the 
manipulation of the draw-tube. 

Under the objective is a brass platform with a hole in the centre 
known as the stage. On this is placed the glass slide containing the 
object to be examined under the microscope. Beneath the stage is a 
mirror capable of turning in all directions, to reflect the light through 
the object. 

The magnifying power of the microscope is obtained by the com- 
bination of objective and eyepiece, and (if necessary) increasing the 
distance between them by using the draw-tube. 

Using a 2 inch objective and a No. 1 eyepiece, the magnification is 
about 60 lineal multiplications, i.e. 3,600 times the real area; but 
magnifications are always expressed as lineal—called diameters. 

Using a 4 inch objective and a No. 3 eyepiece, it is possible to 
magnify to 450 diameters. This is quite high enough for all ordinary 
purposes in textile chemistry. 


160 TEXTILE CHEMISTRY 


To Use the Microscope 


First screw in the objective, insert the eyepiece, and place the 
instrument on a very firm table or bench. Arrange the source of light 
at a suitable distance from the base, and look down the tube with one 
eye. Turn the mirror until the brightest effect is produced. 

Next prepare the slide—instructions for which will be given in the 
proper place—and place it on the stage so that the ends are held by the 
clips, and the portion under the cover glass is over the hole in the stage. 

Look down the tube and carefully turn the rack and pinion until 
the object is nearly focused, then turn the micrometer screw which 
gives the fine adjustment, until the object is exactly focused. 


It requires only practice to learn to correctly manipulate a micro- 
scope, and anyone after a few patient trials should be able to use it. 
Cover glasses should be used always—even over cotton fibres—and it 
is often an advantage to mount the specimen in liquid. 

The microscopic appearance of fibres as represented in textbook 
diagrams is frequently much more ideal than that usually met with, 
and the beginner often fails to recognize the specimen unless it has been 
specially prepared. 

The illustrations here given (Figs. 207-212) are drawings from 
actual photographs of samples as usually met with, and have not been 
specially selected. 


THE NATURAL FIBRES 161 


Slides should be made by teasing out fibres with a needle and 
placing a few in the middle of the glass. <A drop of water, or if the 
specimen is to be made permanent, a drop of Canada balsam in xylol, 


ARTIFICIAL SILK 
pe a 


“a 


UNION CLOTH 
7 ~~ ae 


162 TEXTILE CHEMISTRY 


is put on the fibre and another in the centre of a cover slip, which is 
then inverted and allowed to fall gently on the tuft of fibres. 

A piece of filter paper is put on the top, and gentle pressure is 
applied to the slip to distribute the liquid and to expel excess—which 
is absorbed by the paper. ‘The slide is now ready for examination. 

The student should first prepare slides of known fibres from several 
sources, and secondly examine slides made by others, before he attempts 
to examine the fibres from unknown fabrics. | 

Carefully drawn sketches should be made of every fibre examined and, 
as far as possible, the drawings should be to scale. ‘ 

A microscopic accessory known as a camera lucida is a very great 
aid in this connexion. The form made by Leitz to slip into the top of 
the tube after removing the eyepiece is a very good one. By using 
this addition a sheet of paper can be placed at the side of the micro- 
scope, which appears superimposed on the image when looking through 
the eyepiece. The observer has now merely to look down the tube, 
and by bringing a pencil into the field of view on the paper he can 
sketch over the image as it appears on the paper. 


THE ACTION OF HEAT AND VARIOUS REAGENTS ON FIBRES 


The effect of heat on fibres should be studied by heating a small 
tuft in a narrow test tube. The nature of the gas evolved and the 
appearance of the residue should be carefully noted. 

Sik and wool give off ammonia, and a smell of burnt horn or 
feathers is noticed. Wool sometimes evolves sulphur dioxide after 
liberating ammonia. Cotton yields very little odour, and usually 
evolves an acid gas. 

Acetic acid has no action on cotton, wool, or silk. 

Diluted ammonia 1:1 has also no effect on them. 

Caustic potash or soda (10 per cent.—20 per cent. strength) dissolves 
wool. 

Stronger caustic alkalis, while not dissolving cotton, cause it to 
shrink and become gelatinous on the surface. 

Dilute mineral acids (nitric, sulphuric, hydrochloric) have very 
little effect on fibres until they are removed from the liquid and dried, 
when cotton is converted into hydro-cellulose, which falls to a powder — 
on touching. Wool and silk are not destroyed, but if the acid used is 
nitric, they acquire a yellow colour which is much intensified if the 
fibre is afterwards dipped into ammonia. 

Concentrated acids as a general rule destroy or dissolve all fibres. 
Strong sulphuric dissolves silk in the cold, wool on heating, and causes 
cotton to swell up to a gelatinous mass which is soluble in water. _ 

Bleaching powder, if properly used, does not attack cotton, but 


THE NATURAL FIBRES 163 


wool and silk fibres are both destroyed by it, if the action is continued 
for some time. 

Chlorides of magnesium, zinc and aluminium when dried on the 
fibre liberate hydrochloric acid, which, acting on cotton, destroys it by 
converting it into hydro-cellulose. This action is sometimes used to 
determine approximately the proportion of wool in a union cloth. 


CHEMICAL TESTS FOR THE IDENTIFICATION OF FIBRES 


Many reagents have been suggested for the testing of fibres. 
Detection when fibres of one class are not mixed with those of another 
is, as a rule, not very difficult, and the following scheme is sufficient 
for most cases :— 

1. Heat in an ignition tube—note odour and nature of residue. 

2. Immerse in dilute hydrochloric acid, and when completely 
saturated, remove and dry on an asbestos mat over a small flame 
without charring. 

3. Boil for a few minutes in 10 per cent. caustic soda solution. 

4. Treat with cold concentrated sulphuric acid. 


PROPERTIES OF THE COTTON FIBRE 


In the natural condition cotton fibre (raw cotton) as received at 
Liverpool contains about 


88-89 per cent. cellulose (including ash), 
7-8 per cent. moisture, 
1 per cent. natural wax, etc., 
2-3 per cent. foreign impurities. 


Most of these substances can be separated from the cellulose by 
suitable treatment, e.g. :— 

1. Boiling in very dilute (1 per cent.) caustic soda solution. 

2. Thorough washing in water. 

3. Steeping in strong cold hydrochloric acid. 

4. Very thorough washing until all trace of acid is removed. 

5. Drying in a steam oven. 

The following results were obtained by so treating a sample of 
American cotton straight from the bale on arrival at the Blackburn 
Technical College :— 

Moisture = 7-1 per cent. Cellulose = 89-2 per cent. Impurities 
removed = 3-7 per cent. 

An interesting series of experiments has been conducted in my 
laboratory to determine what influence the various processes through 
which the fibre passes, to make it into yarn, have on the removal of or 
addition to these impurities. | 

The same bale was sampled at various stages, and the samples 


~ 


164 TEXTILE CHEMISTRY 


carefully treated with the same reagents under the same conditions. 
The following results were obtained :— 


Scutched cotton after cleaning and opening— 


Moisture : : : : ; . 43 per cent. 

Cellulose ; : : : : . 90-0 per cent. 

Impurities. : : : : . 65-7 per cent. 
Carded cotton— 

Moisture : ‘ : : : . 43 per cent. 

Cellulose ; ; : : : . 90-0 per cent. 

Impurities . : : : : ..- 6-7 per cent. 
Drawn sliver— 

Moisture : : ; ‘ ° ; 4-3 per cent. 

Cellulose ; ‘ : : ; . 90-0 per cent. 

Impurities . : 5 . : . 657 per cent. 
Roving— 

Moisture : ; : ; ; . 54 per cent. 

Cellulose : : : : : . 90-0 per cent. 

Impurities. - : : . .  46-per cent. 
Mule-spun yarn— 

Moisture ; ; : : : : 4-3 per cent. 

Cellulose : : : : : - 91°35 per cent. 

Impurities. : ‘ : : ‘ 2-35 per cent. 


ce 


After spinning, cotton yarn is “ conditioned,” i.e. treated with a 
fine spray of water to give it the moisture necessary for imparting 
pliability—perfectly dry cotton being brittle. As cotton has hygro- 
scopic properties which enable it to absorb up to 8 per cent. of moisture 
(on the average) from the atmosphere, cotton yarn which contains 
that amount of moisture is called ‘“ natural cotton.” Anything in 
excess is illegitimate. 

Some spinners add calcium chloride or magnesium chloride or both, 
sometimes with, sometimes without, the addition of zine chloride, 
thereby increasing the hygroscopic property of the yarn—which 
enables water to be sold as cotton. 

Yarn should be tested therefore for the presence of “ chlorides ” 
by steeping it in warm distilled water for some time and testing the 
liquor with silver nitrate solution. A white precipitate, insoluble in 
nitric acid and soluble in ammonia, proves the presence of chlorides. 

In some cases it may be desirable, and even necessary, to add zinc 
chloride when conditioning, e.g. in very coarse yarns which will be 
woven up without any application of size and where no antiseptic can 
be added in the usual way to prevent mildew. 


THE NATURAL FIBRES 165 


‘ 


A considerable increase in ‘‘ ash content ”’ indicates presence of 
metallic impurities or adulterations. 

Raw cotton ash is about 1 per cent. on the average. 

Samples examined in my laboratory at various stages in the spinning 
process gave the following results. As before, the samples all came 
from the same bale of American cotton :— 


Raw cotton from bale . : . . 1-43 per cent. 
Scutched cotton. . , . . 1-45 per cent. 
Carded cotton : : : ; . 1-43 per cent. 
Drawn. sliver . : 3 ; : . 1-43 per cent. 
Roving . ‘ ; : . 1-43 per cent. 
Mule-spun yarn : : : : . 1-43 per cent. 


In all cases the percentages are calculated on the dried cotton. 

The actual methods I adopted in making the analyses of the samples 
of fibre were :— 

For Moisture. A light aluminium box about three inches in 
diameter and nearly an inch deep, with a tight-fitting lid, was dried in 
a, steam oven and then weighed on a balance sensitive to one milligram. 
The vessel actually used was a case that had contained Gibb’s den- 
tifrice.. 

It was then filled with fibre—30 grams being used. After weighing 
again it was put into the steam oven for several hours, at the end of 
which time the lid was put on quickly, and when cold the box was 
weighed. The drying process was repeated for an hour, and if a 
further loss was obtained it was reheated until the loss was constant. 

For Ash. The dried and weighed sample was transferred from the 
aluminium dish to a weighed small evaporating dish made of silica, 
and heated over an ordinary bunsen burner (noé a blowpipe) until all 
carbonaceous matter was burned away, and then weighed. A cylin- 
drical screen of metal about six inches in diameter was arranged round 
the dish to prevent draughts carrying away any of the very light 
particles of ash. 

The same method of procedure will be a suitable one for students 
to follow. 

After weighing, the ash can be dissolved in dilute nitric acid and 
tested for chlorides by silver nitrate, and for zinc, magnesium, and 
calcium by the reactions given in Section XII, pages 154-157. 


PROPERTIES OF THE WOOL FIBRE 


Natural wool is a much more impure substance than natural cotton, 
and “ wool washing” is an important Yorkshire industry, the waste 
products from which have been for many years a source of great trouble 


166 TEXTILE CHEMISTRY 


to both washers and public bodies responsible for the prevention of 
pollution of watercourses. 

Raw wool may contain :— 

In the ‘‘ unwashed ”’ condition— 

30 per cent. to 80 per cent. of dirt and other substances remoy- 
able by washing. 

8 per cent. to 12 per cent. of moisture (in warm weather). 

8 per cent. to 30 per cent. of moisture (in damp weather). 

The composition of “raw wool” in the dry condition is usually 
quoted as :— ! 

Yolk and suint, 12 per cent. to 47 per cent. 
Wool fibre, 72 per cent. to 15 per cent. 
Dirt, 3 per cent. to 24 per cent. 

Washing with very dilute alkali or soap is capable of producing a 
wool largely free from grease and filth. Extraction with. organic 
solvents has been tried, but it has not been adopted on the commercial 
scale, owing to the fact that the reagent acts too keenly and spoils 
the natural properties of the fibre. 

A series of experiments conducted in my laboratory with wool 
taken straight from animals reared and grazed on the borders of 
Lancashire and Yorkshire yielded the following results :— 

Raw wool as pulled from fleece 100 gm. 
Raw wool after washing with pure soap, then 

water, and exposing to the atmosphere sat BD aay 
The same washed wool dried at 100°C. till 


moisture was expelled = +. ar 
Ash obtained from same washed and dried sample = 0-6 ,, 
Ash obtained from original wool =a 14:5 ,, 


99 


“‘ Conditioning ”’ is determined by the loss in weight of a sample 
dried at 105°C. to 110°C. 

The methods used for determining moisture and ash in wool are 
similar to those used for cotton. . 
~ Wool, like cotton, is somewhat hygroscopic. The standard allowed 
for natural wool by the Bradford Conditioning House is 18} per cent. 

Silk is the fibrous substance spun by the “ silk worm ” to form its 
cocoon. It resembles wool in many respects. . 

There are. two classes—reared and wild. 

The former comes chiefly from China, Japan, India, Italy, South 
of France, and Greece. 

It is secreted by the grub as two separate liquids which run into 
a common channel at the exit where it solidifies, thus forming a 
uniform double layer. 

This thread is reeled off from the cocoon by putting it in warm 
water to soften the gum with which it is surrounded. As a rule from 


THE NATURAL FIBRES 167 


5 to 20 separate “ends” are collected and reeled off as one thread, 
which may be anything from 1,000 to 4,000 yards long. 

Silk is hygroscopic, particularly in very damp air, and it can absorb 
nearly one-third of its own weight without feeling damp. 

The legal limit for moisture is 11 per cent. 

It-is very elastic and strong and has an average diameter of 0-007 
inch. 

It is composed of silk gum, silk fibre, water, colouring matter, fatty 
materials and mineral (ash). 

The gum is soluble in hot water or soap solution—it forms nearly 
one-quarter of the weight of the raw silk. 

The fibre when purified is found to contain carbon, hydrogen, 
oxygen, and nitrogen. It is called fibroine. 

The ash content should not exceed 0-7 per cent. to 1 per cent. 

Silk is very readily dissolved by cold concentrated hydrochloric 
acid, hot caustic alkalis, basic zinc chloride, and ammoniacal nickel 
oxide solution. , 

It is capable of absorbing large quantities of metallic compounds, 
particularly tannate of iron, with which it is often “ weighted.” 

Determination of the ash content will detect this adulteration. 


SECTION XIV 


THE MACHINERY 


during the latter half of the eighteenth century, and this was 
largely responsible for the removal of the industry from the 
East, South, and West of England to the North. 

The hand loom has now disappeared (except from museums), and 
the power loom has taken its place. Mules are no longer turned by 
hand, and sizing, bleaching, dyeing, and printing are all mainly power 
machine processes. 

Now successful “‘ power ” machinery necessitates :— 

1. Abundant and cheap fuel—such as coal or oil. 

2. Abundant and soft water—for steam-raising purposes, washing, 
bleaching, dyeing, etc. 

3. Efficient lubrication—to reduce friction and wear-and-tear, and 
to increase speed. 

A textile manufacturer who neglects to attend to these essentials 
is giving something away to his competitors. 

Coal should be examined for ash, moisture, and calorific power ; 
and these determinations can be carried out quite easily in any mill 
with very simple apparatus. 

Before testing, the coal should be carefully sampled so as to get a 
truly representative specimen. The sample should be ground up in 
an iron mortar or small grinding mill, mixed by sieving (“‘ 60 mesh ’’) 
and immediately bottled in a well-stoppered vessel. 

To Drrermine MorsturE. Heat between 50 and 100 grams 
in a porcelain dish to 100° C. to 105° C. until no further loss 
occurs. 

The amount present should not exceed 8 per cent. 

To Determine AsH. About 5 grams should be weighed in a 
silica basin and carefully heated over a bunsen flame or in a muffle 
furnace, taking care not to fuse the ash. 

Coal from different sources shows great variation in ash content. 


168 


] textile machinery developed very rapidly 


39 


THE MACHINERY 169 


The following are some results obtained from standard textbooks on 
fuel :— 


36 samples from Wales average 4:91 per cent. 
18 be! » Newcastle + 3:77 m 
28 x », Lancashire " 4-88 _ 
8 * » scotland A 4-03 rf 
7 * 5, Derbyshire Hf 2-65 fe 


15 samples of slack or small coal for stationary boilers :— 

Average = 16 per cent. Lowest = 9-3 per cent. Highest = 22-27 
per cent. 

Cannel Coal—large number of samples :-— 

Highest = 15 per cent. Lowest = 9 per cent. Average = 13 per 
cent. 

Results obtained by me in the examination of samples of coal 
(mostly to be used for firing mill boilers) :— 

Highest, 14:2 percent. Lowest, 4°8 percent. Average, 12 per cent. 

Results obtained in the laboratory of the Blackburn Technical 
College during the past twelve months :— 

No. of samples, 80. Highest, 12:3 per cent. Lowest, 5-2 per cent. 
Average, 9:8 per cent. 

To DretTerMINE CaLoriFIc VAaLuE. When coal burns in air or 
oxygen, or in any other medium capable of sustaining its combustion, 
the chemical changes thereby produced result in the liberation of heat. 
In determinations of calorific value attempts are made to measure 
the amount of heat evolved by the complete combustion of 1 lb. of 
coal. 

Quantities of heat can be expressed in several ways, but for calorific 
values of coal it is most usual to do so in what are known as British 
Thermal Units (written B.T.U.). 

One B.T.U. is the amount of heat required to raise one pound of 
water through one degree Fah. in temperature. 

Occasionally it may be necessary to use other standards ; in that 
event, use the following factors :— 

To convert B.T.U.s to kilogram calories x -252. 

To convert B.T.U.s to centigrade heat units x -55. 

To convert centigrade heat to B.T.U.s x 1:8. 

Calorific values can be calculated by using a formula, but the 
results obtained are not so satisfactory as those obtained by direct 
determinations with a calorimeter. 

The standard form of apparatus is the bomb calorimeter—an in- 
strument based on that of Berthelot, but it is a very expensive appliance 
and is not suitable for mill use. 

The form used in this college laboratory is the Roland Wild calori- 
meter, made by Messrs. Alex. Wright & Co., Westminster, S.W., and 


170 TEXTILE CHEMISTRY 


is a very reliable and not expensive article. (Cheapest form, about 
£6 6s.) 

Fig. 213 shows the instrument in section. The following description 
is copied from the makers’ pamphlet supplied with the instrument. 

The apparatus consists of a combustion chamber A suspended from 
the cover by conduit C, which is furnished with a valve D. 

E is a copper vessel containing water, surrounded by an air chamber 
F to prevent radiation. 

G is a Fah. thermometer graduated in 1/10ths. H is a paddle 
stirrer. The.water value of the instrument is 70 grams. (This has 
been determined by the makers and varies with the instrument.) 

In using this instrument a small quantity of coal is burned in A by 
mixing it with sodium peroxide, the heat evolved from its combustion 
being absorbed by the water surrounding it. If the weight of the 
water be known, and the rise in temperature which it sustains measured, 
then the amount of heat evolved by 
the coal can be calculated, if certain 
corrections be made. 

It has been found, if exactly 0-73 
gram of coal be mixed with 12 to 15 
grams of sodium peroxide and rapidly 
fired—which is done by heating a 
small piece of nickel wire and dropping 
it down the conduit—that the rise in 
temperature of water in degrees Fah. 
x 1,000 


= calorific power of 1 lb. of fuel 
in B.T.U. 


Tis. 213 The coal must be dry when weighed, 

and should pass through a 60-mesh 

sieve. An error of 0-01 gram will produce an error of nearly 1-4 
per cent. in the result. 

The reason for using 0-73 gram instead of 1 gram is that, owing to 
certain chemical changes occurring that are not produced when coal 
burns in air, more heat is registered than is actually evolved by the 
combustion of the coal. The makers have found that this = 27 per 
cent. of the total heat evolved, and they correct for it by using the 
smaller quantity of coal in the experiment. 

The absorption of heat by the calorimeter itself is corrected for by 
using 1,000 grams of water less the water value, in this case 1,000 — 70 
= 930 grams. : 

Through the kindness of the Blackburn Electrical Engineer (Mr. 
Wheelwright), I have been able to check the values obtained by a 


THE MACHINERY 171 


Roland Wild instrument with those obtained from the same coals by 
the bomb calorimeter used at the electricity works. 


Calorific Power in B.T.U.s. 
Sample 
No. 
By Roland Wild. By Mahler Bomb. 
1 10,750 10,800 
2 12,400 12,450 
3 12,150 12,000 
4 12,800 12,750 
5 12,500 12,600 
6 12,700 12,730 
7 10,900 11,000 


A much older, but still very good form of calorimeter is the Lewis 
Thompson, which can be made by any metal worker. A dimensioned 
diagram of the instrument is given in Fig. 214. 

The combustion chamber A is held 
to the base by means of aspring. ‘The “ 
cover Bis attached in a similar manner | 
to the same base. It is provided with | 
a brass tube closed near the top with a | 
tap, and holes are bored near the 10 
bottom. | 

Coal is mixed with an oxidizing sub- 
stance, put into A with a fuse, the 
end of which is ignited. The cover B 
is put on quickly, the tap shut, and 
the instrument lowered into a vessel 
containing a known quantity of water 
at a known temperature. In a few 
seconds the burning fuse ignites the 
mixture and the hot gases produced 
escape through the holes in the cover, 
and passing up the water cause a rise 
in temperature. When combustion is 
complete the tap is opened and water 
then rises up inside the calorimeter, 
thereby absorbing its heat. 

The oxidizing mixture consists of 3 parts of potassium chlorate, 
1 part of potassium nitrate, thoroughly dried and perfectly mixed by 
hand on a piece of paper, not in a mortar. 

For each charge 2 grams of dried coal is mixed with 20 grams of 
oxidizing mixture. 


4 


172 TEXTILE CHEMISTRY 


The fuse is made by soaking cotton wick in a solution of potassium 
nitrate and drying in a steam oven. 

It is desirable to use about 2 litres of water in the outer vessel, 
which should be tall and not very wide, to insure the thorough cooling 
of the escaping gases. 

Then, if no correction is made for heat lost by radiation and absorp- 
tion by the instrument, calorific power of coal in B.T.U. = 


Rise in temperature in ° F. X weight of water in grams 
Weight in grams of coal used } 


As a rule an allowance of 10 per cent. is made to correct for heat 
absorbed by the apparatus, decomposition of substances in the oxidiz- 
ing mixture, and solution of substances remaining. Loss due to 
radiation is compensated for by commencing the experiment with the 
temperature of the water a few degrees below the temperature of the 
room. 

Corrected formula then is :— 


OP. in B..U) = 3 eee 


THE EXAMINATION OF FLUE Gasszs. It is not sufficient for a mill- 
owner to know how much heat his fuel is capable of evolving. He 
should know also how efficiently it is being used. In this connexion 
it is most desirable systematically to test the gases escaping through 
the flues and up the chimney stack. 

If complete combustion of the fuel has been effected, the flue gas 
should contain nitrogen and carbon dioxide only ; as a matter of fact 
oxygen and carbon monoxide are present also. 

A simple but very efficient apparatus designed by the author for 
the analysis of flue gases is shown in Fig. 215. The graduated glass 
vessel A is taken to the flue and filled by suction or other convenient 
means and the screw clips on the pieces of rubber on the ends tightly 
closed. It is then brought to the laboratory or testing room and 
attached to the funnel as shown in Fig. 215. 

Water is run into the funnel B, the rubber tubing squeezed to 
remove any air bubbles, and the clip at the bottom carefully opened. 
The funnel is moved up or down until the water stands at the same 
level in each vessel, and the volume of gas in the graduated vessel is 
noted. 

The clip is closed, the funnel emptied of water and caustic soda 
solution put in. If the level of liquid in the funnel is kept high, some 
of it will be forced into the graduated vessel, when it will gradually 
absorb the carbon dioxide. ‘The rate of absorption may be increased 
by first closing the clip, and then turning the vessel on its side. More 
soda solution is put into B as the liquid passes into A during absorption. 


THE MACHINERY 173 


When absorption appears to be complete, the levels should be 
adjusted again, and the volume of gas now in the vessel determined. 

To estimate the volume of oxygen, the top of the graduated vessel 
should be attached to a similar vessel C (Fig. 216) which is quate full of 
pyro soda solution. When both clips are open and the funnel D 
attached to the vessel C lowered, or that attached to the vessel A 
raised, the gas can be passed completely from one to the other (A to 
C). The clip E is then closed. 


4 
oben a@aame oe 2] 2] 2 eo «2 


Temperature Jacket 


Fie. 215 


After the absorption of the oxygen is complete in C the levels in 
C and D are adjusted and its volume thus determined. 

To absorb the carbon monoxide the pyro soda vessel A is detached, 
and a similar vessel containing a solution of cuprous chloride in hydro- 
chloric acid is attached to C, and the process of absorption repeated 
by passing the gas from C into the new vessel. 

It may be assumed that the residual gas is nitrogen. The experi- 
ment may be performed without “jacketing” the vessels if the 
temperature of the room in which the tests are being carried out is 
constant. Should it vary, it is desirable to arrange a water bath as 
shown by dotted lines in the diagram (Fig. 215). 

In analyses of certain flue gases from mills in this district the 
following results were obtained. They illustrate the great variations 
that may be found. 


174. TEXTILE CHEMISTRY 


Per cent. 


‘ Per cent, 
Sample from Carbon Carbon e | 
Dioxide, | 978°. | monoxide, | Nitrogen. 


No. 4 Boiler (average of 10 expts.) . 9-93 7:5 nil 82-57 
No. 5 Boiler (average of 9 expts.). .| 10:7 6:3 nil 83-0 
Economizers :— 
End ‘near boiler 6:4 ts a 6-4 13-4 1-0 79-2 
End away from boiler . . . . 4-9 14:0 0:6 80-5 
Another mill-boiler flue . . . .{| 10-2 7:5 1:3 81-0 


Boiler feed water should be tested for— 
(a) Total solids. 
(b) Total hardness. 
(c) Temporary and permanent hardness. 
Condensed water should be examined at intervals for— 
(a) Reaction to lacmoid. 
(6) Chlorides. 
(c) Iron. 

Softened water should be examined at regular and frequent intervals 
for— 

(a) Total solids. 
(6) Hardness. 

The instructions for carrying out these tests will be found in 
Section V, pages 43-44. 

Iron is best estimated by a colorimetric process using either 
potassium sulphocyanide (thiocyanate) or, in the absence of lead, 
hydrogen sulphide. 

A measured volume of water is put into a Nessler jar and a little of 
the reagent added toit. Similar jars are filled with the same quantities 
of distilled water to which have been added known amounts of iron 
solution. ‘The liquids which give the same tint of colour on addition 
of the same reagent are assumed to contain the same amounts of iron. 

Boiler compositions are used to precipitate the dissolved solids of 
the boiler-feed water in a friable and easily removable condition. Many 
different substances are used, but the most popular, and probably the 
most efficient, are mixtures of caustic soda and soda ash. 

Proportions that are suitable for one feed water may not be desir- 
able for another, and it would often pay the mill-owner to seek advice 
regarding the best combination to use. 

The following are figures obtained by the analyses of three typical 
boiler compositions of this class :— 

No. 1. Soda ash, 80 lb. Caustic soda, 200 lb. Water, 72 gallons. 

No. 2. Sodium carbonate, 52 lb. Caustic soda, 170 lb. Water, 
75 gallons. 


THE MACHINERY 175 


No. 3. Sodium carbonate, 424 lb. Caustic soda, 39 lb. Water, 
90 gallons. 

Oils form a very important class of mill stores, and all of them 
should be carefully scrutinized before use. 

They are applied in textiles for :— 

(a) Lubrication—e.g. looms, and cylinders of engines. 
(b) Softening wool. 

(c) Giving pliability to cotton yarn. 

(d) Certain mordanting and finishing processes. 

Oils have been extracted from animal and vegetable tissues from 
the earliest times, but during the last hundred years they have been 
obtained also from mineral sources—but these mineral oils are of a 
composition quite different from that of the fatty oils. 

The following table illustrates the usual method of classifying 
oils :-— 


OILS 
Lev, 
Saponifiable Unsaponifiable 
5 BAe | a fetal | 
Animal tissue Vegetable Mineral Rosin Tar Ethereal 
1. Petroleum. 
2. Shale 


Marine Land 
| ea 
Lqd. Oils Solid Fats 


Drying Semi-drying Non-drying Fats 

Oils are all (with the exception of castor oil) very sparingly soluble 
in cold alcohol. | 

Animal oils are usually extracted by rendering (heating to burst 
the tissue). 

Vegetable oils are largely ‘‘ expressed,” although extraction with 
solvents is becoming more important every day. 

These processes may be illustrated on a laboratory scale by the 
following experiments :— 

Rendering. ‘Take a large and deep evaporating dish, half fill with 
water, add pieces of cocoa-nut kernels and boil up. When the oil is 
extracted, cool and skim off the thin layer of solid fat, remelt, cool and 
dry on filter paper. 

Expressing. Make a small press similar to that shown in section 
in Fig. 217. Grind some good-quality linseed in a grinding mill or 
coffee-grinder, and put it in the cavity and screw down the press. 
Collect the oil as it runs out. If it is not quite clear, filter it through 
a dry filter paper. 


176 TEXTILE CHEMISTRY 


Solution. Expression always leaves a certain amount of oil behind 
in the cake—from 5 per cent. to 10 per cent. The cake from the 
previous experiment can therefore be used for this experiment. Fit 
up the apparatus shown in Fig. 218. Put the solvent, which may be 
carbon disulphide, benzene, petrol, or ether in the flask, and the cake 
—after wrapping in filter paper—into the extraction tube. If ether 
or carbon disulphide be 
used the flask should be 


heated on a water bath Condense CE 
shi % To Sink age 


asshown. 'Thestream of ZF 


water through the con- 
denser should be regu- 
lated so that all vapour 
escaping from the extrac- 
tion tube is condensed. 
The solvent passes from 


the tube to the flask 
automatically when the 
level of the liquid reaches 
the top of the siphon 
tube. After collection in 
the flask, the solvent is 
evaporated off and the oil 
remains behind. 

The vegetable and 
animal, or fatty, oils 
used for textile purposes 
include palm, cocoa-nut, rape, soya bean, linseed, castor, cotton-seed, 
olive, whale, and sperm. 

Specimens of all these oils should be examined and some of their 
constants determined. 

Mineral oils are hydrocarbons (Section X, pages 114-117). They 
are not acted upon by caustic alkalis, to produce soaps, and are on 
that account said to be unsaponifiable. 


THE MACHINERY 177 


Rock oils, as they are sometimes termed, are now obtained from 
many parts of the world, and the industry has attained enormous 
dimensions, although it was only in 1859 that the first Pennsylvanian 
oil well was drilled by the modern method of “ tubing.”” These modern 
wells vary in depth, some being 5,000 or 6,000 feet deep. 

The crude oil is fractionally distilled under reduced pressure, the 
different fractions being sold for various trade purposes under different 
names. | 

In Scotland an oil-bearing shale is treated in a similar way, to 
obtain the Scotch shale oils, an industry which commenced in 1847. 


The chief fractions prepared from petroleum oil are :— 
Motor spirit or benzine (at 30° C.-140°C.) sp. gr. -650—-720 
Solvent naphthas . ; : ; 5,  *100--740 
Illuminating oils » °790--825 
Non-viscous spindle oils . A ,,  °850--870 
Viscous machinery oils . : ; : »,  *880--920 
Viscous steam cylinder oils », ° *885—-920 


After fractionating, the oils are “ refined ” by agitation, first with 
sulphuric acid of sp. gr. 1-76 and then with caustic soda (1-2 per 
cent. solution). 

Occasionally oils are found in which the acid has not been 
completely removed, and sometimes one is met with from which the 
alkali has not been washed properly. These are serious blemishes in 
lubricating oils. . 

The examination of oils should include the following determina- 
tions :— 

1. Very accurate determination of specific gravity. This should be 
done at 155° C. or 60° Fah. in a specific-gravity bottle (Section III, 
page 29). Sometimes only a very small quantity of oil is available, 
not sufficient for the usual methods. In that event mixtures of 
alcohol and water should be made until small drops of oil will become 
perfectly spherical in one of them, and exhibit no tendency to rise Or 
sink. The density of this liquid mixture is then equal to that of the 
oil, and can be used in lieu of the oil for filling the specific-gravity 
bottle. 

The following results were obtained by students working in our 
laboratories with bona fide trade samples of oils sold for textile pur- 
poses :— 

Rape = 0-913. Castor = 0-964. Olive = 0-92. Loom = 0-903. 
“ Stainless ” Spindle = 0-91. Neat’s Foot = 0-91. Cylinder = 0-92. 
Sperm = 0-88. 

12 


178 TEXTILE CHEMISTRY 


2. Determination of Ash. The method of doing this has been 
given in Section III, pages 32-33. 

As the ash of oils is very small, and really should be nil, a large 
crucible, or a small silica dish sufficient to hold about 10 grams of oil, 
should be used. 

3. Presence of acids or alkalis. Shake some up with warm water, 
and test the water with— 


(a) Methyl orange—turned pink by mineral acids. 

(b) Phenolphthalein tincture made faintly pink with one 
drop of alkali—decolorized by fatty and mineral acids. 

(c) Phenol phthalein tincture—turned pink by alkalis. 


4, Determination of flash-point. ‘This is the temperature at which 
the vapour evolved from a sample of warm oil will ignite at the surface 
of the liquid when a small flame is put near it. 

There are two variations of the method of performing the experi- 
ment—the “‘ open ” test and the “closed ”’ test. In the former, the 
vessel in which the oil is heated is without lid, and in the latter a lid is 
used in which is a small hole that is kept closed until the temperature 
has nearly reached that at which vapour is evolved. Then it is opened 
for an instant and a small flame applied at the opening. If no flash 
results, it is closed and the process repeated at higher temperatures. 

Standard forms of apparatus are available for performing these 
tests, but as a matter of fact they are not really necessary to get a 
result sufficiently accurate for ordinary purposes. 

The method adopted in our laboratories is to sink a large crucible 
in sand in an iron tray and fill it to within 4 inch of the top with oil. 

If the “ closed test ’”’ is being performed, a small tin lid is put on 
the top. A small hole has been bored in this lid and is closed by 
putting over it a piece of broken electric light carbon (Fig. 219). A 
small flame about the size of a pea is obtained by connecting a mouth 
blowpipe to the gas supply. The thermometer must dip well into the 
oil. When the test is made the gas carbon rod is removed for a second 
with one hand and the flame applied to the hole with the other. If 
the flash-point has been reached a pale blue flame flashes along the 
surface under the lid. ‘The temperature indicated by the thermometer 
is then read, which is the flash-point. . 

In the “ open test ”’ no lid is used and the flame should be brought _ 
near the surface. 

The “ open flash-point ” is higher than the “ closed ’’ one for the 
same substance. If the experiment is repeated, a fresh sample of oil 
must be used, as some of the volatile products are lost to it by the first 
heating. | 

Some results obtained in our laboratory by first-year students :— 


THE MACHINERY 179 


Open Test. Closed Test. 
Description of Sample. 
fl 3} ° Fah, tay ° Fah. 
Suemeoeorg@percik . .*. wet; 256 493 242 468 
2. Cylinder oil es ee SS ewe al We! 423 207 405 
Mere Ol Gk ks 200 392 175 347 
4. 19 OS ae ee 197 387 179 354 
5. Engine oil SS A en rr 220 428 198 388 
MME sf. tk 155 311 145 293 


5. Viscosity determinations. By viscosity is meant the internal 
friction exhibited by liquids. Those possessing the minimum of 
viscosity are said to be mobile. No satisfactory laboratory method 
has yet been devised for measuring viscosity directly. The usual method 
is to measure the rate of flow of the liquid through a small orifice. 
The instrument used is called a viscometer, and the favourite form in 
use in this country is that invented many years ago by Redwood and 
still called by his name. 


His instrument consists of a metal vessel to contain the oil, the 
bottom being provided with a small orifice made by boring a hole 
through anagate cup. This vessel is surrounded by another containing 
water that can be heated by means of a side tube (Fig. 220). The hole 
in the agate is closed by a metal ball, which when raised allows the oil 
to run out into a 50 c.c. flask placed underneath. 


180 TEXTILE CHEMISTRY 


The time of flow is recorded and compared with that taken by 
50 c.c. of pure rape oil. A further precaution is necessary if the two. 
results are to be comparable, namely the heights of the columns of oil 
must be identical. This is provided for by placing a pointer near the 
top of the oil vessel, to the apex of which the level of the liquid is 
adjusted in each case. 

Redwood found that the average time taken by 50 c.c. of rape oil 
at 60° Fah. was 535 seconds. This he called 100 on his scale, and he 
also suggested a correction for sp. gr. 

Viscosity on Redwood scale, using a Redwood viscometer :— 


100 x time of flow xX sp. gr. of oil at temperature of flow. 


535 xX -915 


For approximate work comparisons of viscosities may be made by 
selecting a 25 c.c. pipette, making a mark on the lower stem, and then 
finding the time taken by the oil to run between these two points 
when the pipette is held in a vertical position. 

Another simple form is shown in Fig. 221, made from a piece of 
glass tubing half an inch in diameter, the end being provided with a 
rubber bung through which passes a small piece of capillary tubing. 

Fig. 222 shows the same form of apparatus arranged in duplicate, 
so that comparisons can be made at temperatures differing from that 
of the room. The tubes containing the oil and the efflux capillaries 
must be the same diameter in each case. 


THE MACHINERY 181 


Hig. 223 is a form recently designed by the author for use in his 
laboratory, from which very satisfactory results have been obtained. 

This new form of viscometer consists of an outer glass vessel A, 
in which is a glass tube B, carrying the efflux tube J, and which is 
closed by means of a clip D. 

The oil is passed into the vessel by means of side tube C. When it 
reaches to the top of tube EH, the surplus fluid is carried off through it. 


41 


The thermometer F is so arranged that the bulb is near the efflux 
tube J. 

When carrying out the experiment the clip D is opened, and at the 
same instant the time is noted. The oil is allowed to flow until the 
surface just reaches the point K of the thin glass rod G, and the time 
again noted. 

If, when cleaning the instrument, the positions (in the rubber 
stopper) of tubes E and B and rod G are unaltered, the head (K—H) 
and volume of liquid used are identical for each experiment, and thus 
the relative times of flow will give correct figures for relative viscosities. 


182 TEXTILE CHEMISTRY 


The instrument has given very consistent results and has distinct 
advantages over the Redwood viscometer in certain particulars. 

Viscosities at higher temperatures than normal are made when the 
instrument is surrounded with a hot-water jacket, which is preferably 
heated by means of “live steam.” 

Some results obtained with this viscometer are compared in the 
following table with those obtained at the same time with the same oil 
using a Standard Redwood pattern. 


Time in Seconds. 


Description of Sample. Temp. Ratio 

. : . . Redwood’s.| Cooper’s C/B 
SRG. OU Ge 5 arian. wh or at en ee 415 527 1-27 
Mperin ole 3 ae ee fea eee ees 188 239 1-27 
Tabricating ol! oul. Os: eo ee ee eee 183 232 1-27 
4s es gh ee ee Cre Dees 58 73 1-26 
Spindle oil (mineral). . . . . .| 65°F. 100 126 1-26 
Bs A ap ge Bo ne LA eek cen Oe 55 70 1-27 

. a a Sty ale? Sar eed ea ee aes 40 50 1-26 
Machinery oil (mixed) . . . . .| 65°F. 330 416 1-26 
i é 2 Oe GS 120 151 1-26 

# e. SS 140° F. 63 80 1-27 


Fatty oils and mixed oils are very liable to contain free fatty acid, 
and this should always be estimated to determine the degree of ran- 
cidity of the sample. 

The apparatus used for this purpose is shown in Fig. 224. 

About 10 grams of the oil are weighed into a small flask ; 25 to 50 
c.c. of neutral alcohol are added and the flask and its contents are 
gently warmed in a water bath. 

Standard alkali is put in the burette—usually N/10 caustic soda 
is used—and after the addition of 2 or 3 drops of phenolphthalein to 
the flask, alkali is carefully run in until a pink colour is obtained which 
remains for a few seconds on stirring. 

The strength of the alkali being known in terms of fatty acid, the 
result may be calculated. / 

As a rule acidity is returned as oleic acid, od 1 c.c. N/10 alkali 
— 0:0282 grams of oleic. 

It is also very desirable to know the percentage of saponifiable oil 
present if the analysis is to be a complete one, but this exercise is 
hardly suitable for an elementary worker to carry out, and it is there- 
fore deferred. 


SECTION XV 
SIZING OF COTTON YARN 


OST textile students are aware that sizing commenced 
originally in the early days of cotton manufacture in India, 
but of the actual date when it was first found desirable to 

pass cotton threads through rice water in order to assist in the weaving 
of the fabric, there is no record. 

Dating from that period constant additions to, and many improve- 
ments in, the important process of sizing have been made. 

“Sizing began in necessity, but has ended in something like 
dishonesty,” says a writer on the subject, but he is careful to 
acquit the manufacturer and sizer of the blame for this state of 
affairs. 

It is hardly possible to hope that we shall ever reach the point of 
absolutely perfect sizing, but science has done so much for all branches 
of industry in the past that it is only reasonable to suppose that it will 
be able to do more in the future, and that in this advance sizing will 

share. 
Now the chemistry of sizing—as trades go—is simple. Sizing was, 
and still is, largely empirical; many wonderful mixings have been 
tried and even patented, which in many cases have proved to be more 
or less useless. 

It is only lately that the chemist has been called in to sort out the. 
wheat from the chaff, and to explain the action of the successful 
materials. 

The chemist in his classification of things (see Section IV, pages 
34-35) makes three groups: (1) Elements, (2) Compounds, (3) Mix- 
tures. Of these, class 1 comprises the least in number and the mem- 
bers, as a rule, are the easiest to identify. The second is a very numer- 
ous class, and its members possess the peculiarity of being perfectly 
definite in composition, and consequently they answer to certain well- 
known “ tests” (see Section XII, pages 152-157). 

The third class is by far the most numerous ; it includes nearly all 
common things, and its members are the most difficult to identify. 
There is no fixity or certainty about them—they are constantly 
altering in minor or in important respects. 


183 


184 TEXTILE CHEMISTRY 


Now most sizing materials come under the chemical division of 
mixtures, e.g. flour and all natural grains, tallow, soap, clay, etc. And 
so when we say that the chemistry of sizing is fairly simple, we must 
qualify that statement by adding that the application thereof to sizing 
ingredients is intricate. There is need therefore for the utmost care 
‘and accuracy in testing. 

As a general rule cotton warps are sized, and weft is used in an 
unsized condition. Cotton can be sized in the hank, the ball warp, 
and the tape condition. The reader is referred to books on sizing for 
detailed accounts of these methods. Generally speaking, the size is 
a starch paste to which has been added softening, and sometimes 
weighting, materials. 

The ingredients used for size preparation are usually classified as 
follows :— 

1. Adhesives—starches, gums, etc. 

2. Softeners—tallow, fats, waxes, soaps. 

3. Weighting materials—clay, metallic chlorides. 

4. Antiseptics—zinc chloride, salicylic acid, etc. 

Some ingredients fall into more than one class, e.g. glycerine and 
zinc chloride. | 


FLOUR 


The name flour has no definite significance, it merely means the 
powdered solid obtained from a grain of a starchy nature, and although 
in England we restrict the term to mean the inside of wheat, we do 
not thereby give a much better indication of what it is. 

The substances present in wheat flour are found to be considerably 
dependent upon several very important factors :— 

1. The kind of grain used as seed. 

2. The conditions under which it is grown. 

3. The locality in which it is raised. 

4. The method of milling. 

And last, but not least, the dealer through whose hands it passes. 

In representative samples the contents have been found to be :— 

Starch, which may vary between 60 per cent. and 70 per cent. 

Gluten, which may vary between 2 per cent. and 15 per cent. 
(occasionally up to 20 per cent.). , 

Moisture is about 13 per cent., although the conditions of storage 
can alter this figure considerably. 

Ash should not exceed 0°9 per cent., and it may be as low as 0°4 
per cent. 

A good average is 0-5 per cent. to 0-6 per cent. 

Flour also contains sugar, dextrine, albumen, etc. 

That flour contains starch is easily proved by the iodine test. Boil 


SIZING 185 


a little flour and water and cool it by pouring into a jar of cold water. 
Add two or three drops of tincture of iodine, and a deep blue coloration 
is produced. 

Note.—This colour is destroyed by heating or by the addition of 
caustic soda. Therefore the emulsion must be acid or neutral and cold 
before the iodine is added. Alkalinity should be neutralized by the 
addition of acetic acid. 

The correct estimation of the amount of starch in flour is too long 
and difficult for beginners to attempt, but an approximate method is 
to knead 10 grams of flour in a muslin bag, held in a beaker of water, 
until all the starch is washed out; allow the starch to settle, pour off 
the clear water, dry and weigh the sediment. 


Starch is a naturally produced body, and hence it has a structure. 
Under the microscope this is very apparent and is found to be granular. 
Again, starches produced by different varieties of vegetable tissues are 
found to exhibit different granular structures. 

This forms a ready means of identification. Figs. 225-230 illus- 
trate the microscopic appearance of the most important sizing starches. 

Boiling in water, or the use of certain chemicals, destroys this 
structure by destroying the outer coating of the granule, which is con- 
sidered to be a form of starch cellulose, and which does not produce a 
blue colour with iodine. Starch has no adhesive qualities until this 
coating is destroyed, hence the need for boiling or other treatment 
to make the starch paste. : 

Flour is used in size chiefly as an adhesive, and besides starch it 


186 TEXTILE CHEMISTRY 


contains another constituent which is still more adhesive. This is 
termed gluten, and the value of flour for sizing purposes is largely 
determined by the quantity and quality of the gluten Presene A good 
average is 9 per cent. to 10 per cent. 

As a great deal of gluten is often lost in fermentation (see 
pages 200-201), the quality is of more importance than the quantity. 
_ This must be tested when moist after washing away the starch. It 
should be tough, tenacious, and elastic. 

A simple and often valuable test to apply to a specimen, to indicate 
whether the powder is starch or flour, is to add two or three drops of 
strong nitric acid to some of it placed on a white porcelain lid. 

Flour is turned yellow, starch becomes a greyish white translucent 
mass. 

Although flour is not so largely used as formerly, it is still a very 
important sizing ingredient and is nearly always used (alone or in 
conjunction with other starches), when it is desired to add weight to 
the yarn. Before use it must be prepared, which is done by fermenting 
it after mixing with an equal quantity of water, or by pd a in a 
solution of zine chloride. 

Fermentation may extend over months, but steeping is considered 
sufficient if it has lasted two or three weeks. This treatment separates 
the granules, destroys the stickiness, and dissolves the glutinous 
products. 


FARINA 

This term is a trade name for potato starch. A potato contains on 
the average 75 per cent. water, 20 per cent. starch, and 5 per cent. 
other substances. If potatoes are pulped and washed, the starch can 
be obtained from them in an almost pure condition. 

It is dried carefully at a low temperature, so that it retains about 
17 per cent. to 20 per cent. of water. 

Farina is characterized by its glistening appearance, its crisp feel, 
its large granules, and the thick paste it forms with water when 
gelatinized. 

This starch should always be examined under the microscope ; the 
more uniform the granules the better the quality as arule. Very large 
granules are not desirable, and a large number of very small ones 
indicates that the potatoes from which it was manufactured have not 
matured. Pastes made from these farinas soon lose their adhesive- 
ness and “ fall away.” 

Even the best farina is liable to exhibit this defect of rapidly 
deteriorating after making up for size. It can be prevented somewhat 
by adding a very small amount of caustic soda to the water before the 
starch is boiled in it. 


SIZING 187 


The ash from farina should be so small as to be almost unweighable 
if 20 grams or so are completely ignited. 


SAGO 


Sago flour is very largely used in North-east Lancashire. In spite 
of its somewhat yellow natural appearance it is greatly esteemed as a 
sizing starch, because it greatly strengthens the yarn and allows it to 
stand a “ high pick.” 

Sago is a starch obtained from the pith of a plant of the palm 
family, and was first used—according to a Patent Specification—in 
1860. 

The pith is pulped and stirred in water over a sieve. The starch is 
thus washed out and passes through the holes while the fibre, etc., is 
retained. It is then air-dried and shipped. 

On reaching this country it is “ dressed > by means of silk sieves. 

It is usually a nearly pure starch, but the ash is higher than with 
farina, and is sometimes of a gritty nature. 

It presents a very typical appearance under the microscope (Fig. 
927, page 185). The ends of the granules are distinctly truncated. If 
too much sago is used in size mixings, the warps are made too stiff, 
which, if not apparent to the touch, makes its presence evident by 
cutting the healds. | 

On this account it is usual in the Nelson district to steep the sago 
overnight in cold water and boil up in the morning. The boiling 
should be more prolonged than with farina. 

Low-grade sago flour is liable to be contaminated with sea water. 
It is therefore necessary to test samples for the presence of chlorides. 


MAIZE OR CORN STARCH 


This starch is produced in enormous quantities in America, where 
methods for its extraction have been brought to a high state of per- 
fection. Many years ago there was considerable prejudice against this 
starch as a sizing ingredient, but to-day it is much more popular, 
particularly the better brands. 

The paste produced from it is very thick, opaque, and somewhat 
liable to mildew rapidly. When dried it has a harsher feel than that 
of most other starches, but it is very adhesive and may be boiled for a 
long time with “open” steam without fear of deterioration. This 
boiling tends to reduce its natural harshness. 

Maize starch is often used in conjunction with flour for heavy sizing. 

During the period of the war, when farina was almost unobtainable, 
it became necessary to use it in “ pure ” and “light” sizing, and in 
many cases it is still being retained—so satisfactory has it proved. 

Corn starch should be carefully scrutinized under the microscope, 


188 TEXTILE CHEMISTRY 


and a sample showing small and regular granules will be found as a 
rule to give the better results. The ash should be practically nothing. 

Many proprietary brands of starchy materials contain maize starch 
as one of the ingredients. 


CASSAVA 


This is a “root” starch produced largely in South America. It 
is prepared as a food starch under the name of tapioca. It is seldom 
that the cotton manufacturer buys it in the pure form, although he 
certainly gets it in certain sizing starches that are sold under special 
trade names. 

Cassava under the microscope appears in somewhat hemispherical 
granules (Fig. 229, page 185). They gelatinize readily to produce a 
thin and not particularly adhesive paste. 


RICE 


Rice starch is chiefly used as a laundry starch. The qualities 
which make it desirable for this application are those which militate 
against its use as a sizing starch. 

The granules are small, harsh, and when dried produce a very rough 
yarn and a cloth of “ boardy feel.” 

Many sizing flours contain small proportions of rice flour or rice 
starch, these admixtures enabling the user to obtain various cloth 
effects, particularly in regard to feel. | ) 


LABORATORY EXERCISES IN THE EXAMINATION OF STARCHES 


1. Test solubility in cold water by shaking, filtering, and testing 
the filtrate with tincture of iodine. 

2. Put a few drops of a cold emulsion in boiling water. Allow it to 
cool—note if a jelly is produced. Take some of this in another tube, 
shake up with more cold water, add iodine, and note production of 
the blue colour. Boil some of this and note that the colour disappears 
and probably returns on cooling. 

3. To some starch paste add a few drops of caustic soda solution. 
Test a portion of this with iodine—no blue colour is produced. 
Neutralize another portion with acetic acid and then add iodine— 
the blue colour appears. 

Therefore, to test for starch always proceed as follows :— 

Shake up the substance in cold water, boil the mixture, test with 
litmus paper to determine if it is alkaline. If so, neutralize with 
acetic acid, cool the liquid, and then add a drop or two of tincture of 
iodine. If it turns blue, starch is present. 

4. Determine the percentage of ash and water in starches. (See 
Section III, pages 31-33.) 


SIZING 189 


Examine permanent slides of various starches under the microscope 
and try to identify them. Carefully sketch in your notebook the shape 
of the granules of each variety. 

Prepare samples of starch for examination under the microscope :— 

Add about enough starch to cover a sixpence to a test tube half 
full of cold water; shake well and take out one drop on the end of a 
glass rod. Put this on the middle of a clean microscope slide and 
carefully drop on it a glass cover slip so that no air bubbles are held 
under it. Place on top a piece of filter paper and gently press. 

Prepare in this way samples of farina, flour, maize, and sago ; and 


- also farina which has been boiled. 


Flour should be tested for mineral impurities, other starches, and 
mildew. 

An increased ash content indicates mineral adulteration, which 
may also be detected by shaking up the flour in a test tube with 
chloroform, when the clay, gypsum, etc., settles to the bottom, while 
flour floats. 

Maize, rice, tapioca may be readily detected under the microscope. 

Another valuable test to apply to flour is to add to 20 grams of 
flour a mixture of 70 c.c. of absolute alcohol, 25 c.c. of water, and 5 c.c. 
of strong hydrochloric acid. Put it in a large tube and digest in a 
beaker of hot water for some time. Allow it to stand to cool for an 
hour. 

Examine the appearance at the end of that time. If the liquor is— 

(a) Perfectly colourless, it is pure wheat flour ; 

(b) Blood red, it contains ergot ; 

(c) Purpie red, it contains mildew ; 

(d) Yellow, it contains barley or oat flour ; 

(e) Orange yellow, it contains pea flour. 

To determine the amount of gluten in flour :— 

Weigh out 20 grams of flour, put it in a 4-5 inch evaporating basin, 
and add water a few drops at a time, stirring with a glass rod until it 
is made into a lump of dough, not a paste. With a little practice, and 
if too much water is not added, it is possible to gather every particle 
of the flour into one ball on the end of the glass rod. 

Take a piece of washed cotton cambric of moderately low texture 
(say 40 picks to the inch) about 6 inches square, and after thoroughly 
wetting it, put the dough in the middle, tie up tightly with string— 
allowing plenty of room for the flour to swell—and knead in a basin 
of water or under the tap until all the starch is washed out. 

This point is reached when the water runs perfectly clear from the 
bag. The kneading must be thorough, but care must be taken that 
nothing is forced through the bag, which should now contain the gluten. 

Open the bag, carefully collect the gluten into one lump, and roll 


190 TEXTILE CHEMISTRY 


it between the palms of the hands until it begins to stick. At this 
point it should be weighed on a small piece of aluminium, and the 
weight recorded as “ wet gluten.” 

It may now be dried in a steam oven (a process which may take 
several days), when it will be found that in the wet condition it weighs 
2-64 times its dry weight. Consequently, if an early result is required 
it is usual to weigh wet and divide this weight by 2-64. 

The quality of the gluten may be determined by stretching the mass 
as it is being dried between the palms of the hands. 

Students are advised to make mixtures of genuine flour with other 
starches, particularly maize, and note the difference in appearance 
and adhesiveness of gluten obtained therefrom. 

Softeners. Ingredients of this class are added to counteract the 
harshness which would be produced in the fibre by coating it with 
pure starch. Many fats and oily substances are used, of which the 
following are important :— 


TALLOW 


Tallow is a well-known natural fat extracted from the sheep or ox. 
In the animal the fat is contained in little bags called sacs, and the 
tallow-chandler has to get it free from this membrane, which is not 
composed of fat. 

This is termed rendering. The old process was to melt over a fire 
and press the fat, which will never produce a white tallow—and the 
method is now practically extinct. 

The modern process is to extract with steam at a pressure of about 
50 lb. to the square inch. The principle of the method is shown in 
Fig. 231. The fat is placed in an iron cylindrical chamber, provided 
with a wooden floor and two doors—one at the top and one near the 
bottom. Through the chamber runs a pipe that conveys the steam, 
which escapes from it at intervals. This melts the fat which rises to 
the top and can be drawn off at the delivery taps. The bottom door 
is for the removal of the membranous residue. A safety valve is put 
on the top of the vessel. 

By this method, if good and fresh materials have been used, a good 
and nearly pure tallow, free from dirt and foreign matter, will be 
obtained. It is evident, therefore, that very little skill and only simple 
apparatus are required to produce good tallow ; but many things affect 
the quality before it reaches the user, e.g. :— 

Hardness depends upon the breed, age, food, and sex of the animal. 
Oil-cake feeding gives a softer fat than grazing the animal. 

Acidity is the result of age ; mutton tallow goes “rancid ” sooner 
than beef tallow of the same quality. Two explanations to account 
for this acidity have been advanced :— 


SIZING 191 


1. When exposed to air it undergoes change due to the action of 
ferments, whereby acids are produced. 

2. In the presence of light and oxygen (in air) certain constituents 
of the tallow are oxidized to acids. 

At the present time, the second cause is considered to be the more 
potent. 

Water present is largely determined by the honesty or dishonesty 
of the renderer. The addition of a small amount of caustic potash 
during rendering—which produces a potash soap—greatly assists the 


“Steam 


Fig. 234 


* tallow to absorb water as it sets. Such tallow will give an alkaline 
reaction with the usual indicators. 

Some characteristic Properties of good Tallow. All pure fats should 
be odourless, tasteless, colourless, and should not darken when exposed 
to air. The nearer tallow approaches to these qualities, the purer it 
is as a rule. All taste, colour, and smell are due to the presence of 
small quantities of substances other than fat. 

Fat should be neutral when in solution, e.g. if some tallow be 
dissolved in’ ether, divided into two portions, and a piece of red 
lacmoid paper be placed in one and blue in the other, there should be 
no alteration in either. 

Tallow is completely soluble in carbon disulphide, chloroform, ether, 
and alcohol. It is insoluble in water, but is capable of absorbing water. 
If the fat be melted in a long tube which is kept hot by surrounding it 
with a hot-water jacket (Fig. 232) the two liquids will separate—tallow 


192 TEXTILE CHEMISTRY 


collecting at the top, water at the bottom. If the tube is graduated 
it is very easy to calculate the proportion present. 

This is due to the fact that, bulk for bulk, tallow is lighter than 
water. The sp. gr. of tallow is not a constant quantity for all 
samples. 

Beef tallows at 15° C. range from 0-925 to 0-953. 
Mutton ,, ., . », 0:937 ,, 0-960. 

A good average is 0:94. 

If determined in the liquid condition at 100° C. and compared with 
water at 15° C. the range is from 0-885 to 0-863. 

The melting-point should be 111°-113° Fah. or 44—45° C. 

Beef tallow may range from 42-6° to 50°C. As it gets older it falls, 
but never below 40° C. 

Mutton tallow has a melting-point of about 47°C. As it gets older 
it tends to rise. 

The Testing of Tallow. A great deal of useful information respecting 
a tallow can be obtained by performing the following experiments 
with it :— 

1. Find its melting-point. (See Section III, page 28.) 

2. Test its solubility in chloroform or carbon disulphide. Any 
insoluble matter is an impurity. 

3. Test the solution as obtained above with (a) lacmoid, (6b) methyl 
orange. The latter will detect mineral acids, and the former free fatty 
acids or alkalis. 

4, Dry and weigh a small evaporating basin half full of small 
pieces of pumice. Add a few grams of tallow, and heat in a steam oven 
for several hours until the loss is constant. The loss is due to expulsion 
of water. 

5. Boil some tallow with dilute nitric acid, cool to solidify the fat, 
filter and warm some of the filtrate with ammonium molybdate 
solution. A distinct yellow coloration or precipitate indicates a 
phosphate—which is due to the presence of bone fat. 

6. Burn a weighed quantity in a crucible and find the percentage 
of ash present. From pure tallow it is almost nil. 

7. Boil two or three drops of tallow with alcoholic potash solution 
for several minutes and then add an equal quantity of warm water. 
A white turbidity or precipitate indicates the presence of paraffin oil 
or paraffin wax, or similar adulteration. 


SOAP. 


Soap is a substance which has been known from very early historical 
times. We find it mentioned in literature which is quite 2,000 years 
old, and during recent years a soap factory has been discovered in the 
remains of Pompeii. . 


° 


SIZING | 193 


Except that the manufacturer has discovered how to add things 
which are not soap, the process of making is almost identical with 
that of the ancients. 

There are two sorts of soap: (1) Hard or soda soaps; (2) soft or 
potash soaps. In all cases it is made by the action of an alkali on a fat 
or fatty acid or oil. A fat is acompound which can be split up into a 
fatty acid and glycerine. 

The alkali neutralizes the acid in the fat and liberates glycerine. 
The neutral product is called a soap, which is essentially the sodium 
(or potassium) salt of the fatty acid. 

On a small scale soap may be prepared in the following ways :— 

1, Shake up ammonia with olive oil—a white solid results which is 
largely soap. 

2. Make a strong solution of caustic soda; add this to palm oil, 
stir well, and allow it to stand. In a short time the temperature rises 
and solid palm oil soapis formed. This is known as the “ cold process ” 
of soap-making. 

3. Make a solution of tallow in alcohol, add some caustic soda 
previously dissolved in water, and simmer on a water bath for half an 
hour. Add salt to the liquid, and soap is precipitated from solution. 

Soaps as now manufactured contain (if unadulterated) from 40 per 
cent. to 50 per cent. of moisture, from 40 per cent. to 45 per cent. of 
fatty acid, from 7 per cent. to 10 per cent. of combined alkali, and very 
little free alkali. 

Yellow soaps contain resin, mottled soaps iron, and an almost 
endless list of adulterants and additions has been compiled. Starch, 
clay, talc, chalk, oils, sugar, sulphur, sand, etc., etc., are some of these 
additions which may be added to produce a soap suitable for some 
special purpose. 

Pure hard soap contains 31 per cent. of water—it is impossible to 
make it with less. If it does not yield this quantity it has been 
dried since manufacture. Soap-flakes often contain less than 10 per 
cent. 

In cocoa-nut oil soap the water may reach 75 per cent. to 80 per cent., 
and it may still appear a fairly solid soap. 

The analysis of a good sample of soap yielded the following results : 
55 per cent. fatty acid, 9 per cent. fixed alkali, 36 per cent. glycerine 
and water. 

The value of a soap is largely determined by the quality and 
quantity of fatty acid present ; any hard soap with more than 64 per 
cent. has been dried, any with less has been intentionally reduced. 

Free alkali, which may be detected by adding a drop of phenol- 
phthalein to a freshly cut surface, when a pink colour is produced, is 
not—except that it indicates a badly made soap—very objectionable 


18 


194 TEXTILE CHEMISTRY 


from a sizing point of view. In fact, a slight alkalinity in soap will 
neutralize undesirable acidity in a rancid tallow. 

The chief reason for using soap in a size mixing is that its presence 
assists in the more perfect emulsification of the fat and thus a more 
uniform liquid is produced. 

Some sizers use no soap as such, but they add a small sana of 
caustic soda. During boiling this alkali reacts with some fat to form 
soap, and therefore they are using it although not adding it as a separate 
ingredient. Soap is also present in many trade softeners and sizing 
compositions. 

Soap must not be used in the presence of metallic chlorides or some 
of the value of each is destroyed. 

For sizing purposes a good soft soap or a hard soap made by the 
cold process is to be preferred to an ordinary hard soap, as soft soaps 
and cold-process ones often contain all the glycerine present in the 
original fat. 

The testing of soap should include these determinations :— 

1. Water. Take a sample from the middle of the bar if hard, or 
below the surface if soft. Weigh quickly on a tared watch glass and 
then shred it if hard soap, and dry in an air oven at a temperature of 
105° C. till no further loss in weight occurs. Calculate to a percentage. 

2. Find the amount of ash. (See Section III, pages 32 and 33.) 

3. Fatty acid. Weigh out 25 grams of the sample and dissolve 
in a beaker of water on a water bath. When it is near boiling-point add 
a few drops of methyl orange, and then strong hydrochloric acid till 
the indicator has been turned a distinct pink colour. This liberates 
the fatty acid. Boil gently till the acid forms as an oily layer on the 
top of the liquid. 

Add 5 grams of stearic acid or paraffin wax, warm up until the two 
are thoroughly mixed, and then allow the vessel and contents to cool. 
Carefully remove the cake, dry on filter paper, and weigh. Deduct 
the weight of wax (which was added to ensure that it set solid) and 
calculate to a percentage on the amount of soap used. 


GLYCERINE 

This substance has a certain application in sizing—less, probably, 
than it deserves—as besides acting as a softener it is nyeronens and 
has mild antiseptic properties. 

Glycerine may be obtained from fats by subjecting ‘heat to the 
action of superheated steam at a temperature of 300° C., but as a rule 
most commercial glycerine is obtained as a by-product in the two 
industries of soap-making and candle-making. 

This glycerine is often contaminated with many undesirable 
substances, and is very dark in colour—sometimes almost black— 


SIZING 195 


and although then cheap, it is useless to the sizer on account of the 
darkening effect it would produce in the size. 

If, however, it is only slightly brown it may be used, provided 
certain impurities are absent. 

As good glycerine is expensive, many “ glycerine substitutes ” are 
on the market; these are often only solutions of glucose sugar, and 
are almost useless for sizing purposes. 

Glycerine mixes in all proportions with water and alcohol, but is 
insoluble in carbon disulphide and chloroform. Taste is a very good 
test to apply to glycerine—if impure, it is distinctly unpleasant. 

A good sample of commercial glycerine yielded the following 
results on analysis :—Sp. gr. 1-3, 80 per cent. to 82 per cent. real 
glycerine, 10 per cent. ash, and gave no precipitate on being added to 
strong hydrochloric acid. 

The Testing of Glycerine. Sufficient information as to its suitability 
for use as a sizing ingredient will be obtained by performing the 
following experiments :— 

1. Find its sp. gr. (See Section III, pages 29 and 30.) 

2. Add some to an equal volume of strong hydrochloric acid in a 
test tube. Invert the tube two or three times to thoroughly mix the 
two liquids, and then allow the mixture to stand for half an hour. If 
at the end of that time no white precipitate has been deposited, it 
may be assumed that salt is not present in sufficient quantity to 
condemn it. 

3. Test for presence of glucose by diluting with an equal volume 
of water and then boiling it with some Fehling solution. If sugar is 
present the blue colour is destroyed, and a red precipitate is produced. 

4. Test for lime by adding some crystals of ammonium oxalate 
to some which has been diluted with twice its own volume of water. 
Shake well at intervals—a white precipitate indicates the presence of 
_ salts of lime. 


WAXES 


Chemically, waxes are quite distinct from fats, but the classification 
is not based on their physical state, e.g. Japan wax is really a fat, 
and sperm oil is a wax. 

Of the substances commonly known as waxes, the ones used in 
sizing are :—Japan wax, paraffin wax, spermaceti, and wool grease. 

Japan wax and spermaceti are both expensive substances and are 
used in very small quantities in mixings ; their use seems to be “ faddy ” 
rather than essential in many cases, but spermaceti wax and paraffin 
wax crystallize from tallow and in some pure mixings are used by 
reason of this property, as thereby a peculiar feel and appearance are 
obtained. : 


196 TEXTILE CHEMISTRY 


Japan wax has a high melting-point and is sometimes used for cloth 
sent to hot and very humid countries, e.g. Java. 

Paraffin wax and wool grease are much more widely used, and in 
some cases they are very desirable or even necessary ingredients, but 
the former is a very dangerous ingredient to put into size if the cloth 
is to be afterwards bleached or dyed. 

Because of the extraordinarily high price of tallow now prevailing, 
many manufacturers have been induced to use other forms of grease. 
One of the most successful has been wool grease, the best qualities of 
which are not usually sold under that name. 

This substance is excreted through the skin by sheep and collects 
in the wool by absorption. In wool washing it is extracted in a very 
impure condition. When highly purified a very valuable neutral wax 
is obtainable which is sold under the name of Lanoline, and has been 
largely used in the preparation of ointments, due to the very char- 
acteristic property it possesses of being readily absorbed by the 
skin. 

The crude “ recovered”’ or ‘‘ Yorkshire”’ grease is a mixture of 
free and combined fatty acids and alcohols. It is a dark yellow or 
brown viscous substance of melting-point 39°C. to 42°C., sp. gr. 
0:973 at 15° C., and has a distinct smell of sheep. 


CHINA CLAY 

Of all weight-giving substances used in sizing none is so successful 
as good China clay. 

Magnesium sulphate, gypsum, barytes, and other compounds have 
been used, but it has been demonstrated to the sizer that it rarely 
pays to use them except for the more common kinds of cloth. 

In nearly all parts of this country clay is found in the soil, but in 
only a few districts is it of the kind necessary for the sizer’s use, i.e. 
kaolin or China clay. 

This kind is found in geological deposits in Cornwall and Devon, 
where older rocks have been weathered and destroyed, and the small 
particles of aluminium silicate have been collected by the action of 
water. The deposits have become dry, and thus form the natural beds 
of clay. 

These beds contain particles of sand, mica, and iron salts which were 
present in the original rock. The method of treatment is to mix up 
the mineral with water : the clay, being lighter than sand, remains in 
the top layer of liquid, which is run off and then allowed to settle. 
If this is repeated several times a clay free or nearly free from impurities 
is obtained. It is then dried in kilns. 

Physically, clay is a very fine white powder, which has a great 
capacity for absorbing water, and, owing to this absorption and its 


SIZING 197 


fineness, becomes plastic. It is soft and soapy to the touch, and when 
breathed upon it emits a characteristic earthy odour. 

For sizing purposes it should be free from iron, grit,and lime. It 
should possess also an unctuous feel—plasticity is not the quality 
desired. It should not be coloured artificially. 

The amount of moisture present in commercial China clays often 
varies very considerably. This is due generally to imperfect drying ; 
but even if the clay be thoroughly dried at steam heat, a certain 
amount of water remains, varying from 10 per cent. to 12 per cent., 
which is only expelled at red heat. 

For heavy sizing especially, it is very desirable that the sizer should 
know the excess of moisture above this 12 per cent., which might be 
called the “‘ strength ” of the clay. This may be determined by drying 
in a steam oven, or better, at 105° C. to 110° C. for several hours, until 
the loss is constant. An aluminium tray is a suitable receptacle to 
use for the purpose. 

The sizer whose speciality is heavy sizing would do well to determine 
the percentage of “ free ” (i.e. expelled at 105° C. to 110° C.) and ““ com- 
bined ” (expelled at red heat) moisture in his various samples of clay. 
An example of this is given on page 33. 

Mellor states that the best temperature at which to determine 
“ hygroscopic ” (i.e. free) moisture is 109° C. to 110° C. For the loss on 
ignition (i.e. combined moisture) for Cornish China clays, previously 
dried at 110° C., he gives the following figures :— 


reas ae per cent. | mhese calculations are 
Mean of six ; j 12-5 # is made on the dr ied, 
Ideal Bn ee not natural, clay. 


LABORATORY EXERCISES WITH CHINA CLAY 


1. Test for chalk by adding hydrochloric acid. If present, effer- 
vescence will result. Filter, and to the filtrate add ammonium 
oxalate—a white precipitate is obtained if chalk, or plaster of paris, 
or gypsum is present. 

2. Grit should be detected by shaking a few grams with water, 
allowing the mixture to stand for two or three minutes, pouring off 
the top layer, and examining the sediment. This may be done by 
rubbing it between two glass microscope slides or by examination 
under the microscope. 

3. The presence of artificial colouring may often be detected by 
adding a few drops of strong ammonia and stirring with a glass rod. 

4. Boil some with hydrochloric acid, filter and divide it into two 
parts. To one add potassium ferrocyanide—a blue colour is produced 


198 TEXTILE CHEMISTRY 


if iron is present, the depth of tint depending upon the quantity in 
solution. A clay suitable for sizing purposes will show only a faint 
colour. 

To the other portion add ammonia and boil. A reddish brown 
precipitate indicates the presence of an undesirable amount of iron 
in solution. 


METALLIC CHLORIDES 


These substances are used to give either weight or antiseptic 
properties, or both, to the twist. 

Those most frequently used are (1) zinc chloride; (2) magnesium 
chloride ; (3) calcium chloride. 

Beside these, another sometimes gets into the size—due to adultera- 
tion of ingredients—i.e. (4) sodium chloride. 

Of these, the only antiseptic is zinc chloride. Zinc chloride, mag- 
nesium chloride, and calcium chloride are all deliquescent bodies 
(i.e. they abstract moisture from damp air). 

Calcium chloride and sodium chloride are not desirable ingredients 
to have in size except in very small proportions. 

Zinc chloride is made on the commercial scale from scrap zine or 
zinc ashes and skimmings or compounds of the metal that have been 
produced as by-products in certain manufacturing processes, by 
mixing the raw material with hydrochloric acid. The resulting liquor 
is treated to free it from iron and other undesirable impurities and 
concentrated to a syrup-like mass containing about 45 per cent. of 
anhydrous chloride of zinc, having a sp. gr. of 1-51—-1-52 (102-104° Tw). 

For export it is usually evaporated till nearly all the water is ex- 
pelled and it sets as a white solid containing zinc equivalent to 98 per 
cent. or more of zinc chloride. 

Commercial zinc chloride is seldom pure, as the cost of removal of 
all impurities would make it a very expensive chemical; nor is it 
necessary for sizing purposes that this highest degree of purity be 
attained. It is sufficient as a rule that free mineral acid and iron be 
absent, and that less than 1 per cent. of sodium chloride be present. 

The tests for these impurities may be conducted in the following 
manner :— 

1. Salt or Sodium Chloride. Pour some into a test tube half 
full of strong hydrochloric acid, and after mixing allow it to stand for 
half an hour. [f salt be present to a greater extent than 1 per cent. 
it will be precipitated in small white crystals. 

2. Iron Salts. Boil a few drops with pure nitric acid and then 
add one drop of it (on the end of a glass rod) to some potassium 
thiocyanate solution in another test tube. The production of a blood- 
red colour shows the presence of iron. The depth of the colour depends 


SIZING 199 


upon the amount of iron in solution—if it be but faint the sample may 
be passed as fit for use. 

9 Free Acid. The indicator used must be either Congo red 
paper (which is turned blue), or methyl orange solution (which is 
turned pink) by free mineral acid. As a rule the manufacturer tries 
to produce a solution which is slightly basic in character, that is, it 
contains a little oxychloride of zinc in solution. 


LABORATORY EXERCISES 


I. Examine samples of zinc chloride, (a) solid, (6) in solution ; and 
perform the following experiments with them :— 


Solid 


1. Expose to air on a watch 
glass for half an hour ; note what 
happens. 

2. Test solubility in a small 
quantity of water. 

3. Note effect of adding more 
water to this, then addition of 
dilute hydrochloric acid. 

4. Take a small piece in a 
porcelain crucible ; heat strongly 
and note all changes. 


Solution 


1. Test for zinc by adding am- 
monia and ammonium sulphide. 

2. Test for salt by adding some 
to an equal quantity of strong 
hydrochloric acid. 

3. Test reaction to litmus, meth- 
yl orange, and Congo red. 

4. Test for presence of iron by 
potassium thiocyanate. 

5. Test for calcium by adding 
ammonium chloride, ammonia, 


and ammonium oxalate. 


II. Heat some zinc oxide on charcoal with the mouth blow-pipe, 
using the oxidizing flame. Note colour—hot and cold. When cold, 
moisten residue with a few drops of cobalt nitrate solution. Reheat, 
and again note the colour. Repeat the experiment, using in turn, 
on a fresh spot on the charcoal: alumina, magnesia, clay, “ anti- 
septic,” “zinc,” “* septic.” 

III. Prepare a solution of zinc chloride by dissolving zinc powder 
or granulated zinc in commercial hydrochloric acid, using excess of the 
metal. When action has ceased filter through glasswool (It will 
dissolve filter paper) and concentrate to a syrup. Find its specific 
gravity, and test it for the presence of free acid and iron. 

Magnesium Chloride. This substance is a white crystalline, 
very deliquescent salt, the chief source of which is the enormous 
Stassfurt deposit in Germany—not far from Jena. From these mines 
it comes into commerce in an exceedingly pure condition. 

In our own country there are large deposits of dolomite and mag- 
nesium limestone—which are compounds of lime and magnesium 
carbonates. Upon treating with hydrochloric acid the carbonates are 
converted into chlorides. The magnesium chloride is less soluble than 


200 TEXTILE CHEMISTRY 


the calcium (lime) chloride, and is crystallized out first. By this method 
of preparation the chloride of magnesium always contains chloride of 
calcium as an impurity. 

It can be detected by adding to a solution of magnesium chloride 
the following solutions in the given order :—Ammonium chloride, 
ammonia, ammonium oxalate. Gently warm. A white precipitate is 
formed if calcium chloride is present. 

Magnesium chloride is cheap, very deliquescent, and thus gives 
weight to the yarn or cloth, but it must not be used in the presence of 
soap, or without the addition of an antiseptic, as magnesium chloride 
itself is not one. 

Calcium chloride must not be confused with bleaching powder 
_—which is not, strictly, chloride of lime at all, although often so 
‘called. This is not a suitable compound to use in size mixings— 
lime salts never are. It is very cheap, being formed as a by-product 
in many chemical industries, and thus it is often used to adulterate 
other chlorides. 

It is very deliquescent, but has no antiseptic value, and it must not 
be present in mixings that contain soap. 


FERMENTATION, MILDEW, ANTISEPTICS 


For perhaps thousands of years it has been known that if a sugar 
solution be exposed to air and warmth it is gradually converted into 
a liquid having very different properties, and that if this liquid be 
further exposed it becomes sour. 

Later it was noticed that bubbles were formed during the process, 
and hence arose the term fermentation. Attempts to explain why 
wine was converted into vinegar were made as early as 1670; and Dr. 
Willis (who died in 1675) considered that all vital actions were due to 
different kinds of fermentation. 

Liebig investigated many cases of fermentation and came to the 
conclusion that the process was due to the action of ferments. It 
remained for Pasteur to experiment exhaustively in the subject, and 
as a result of his researches he advanced the view that fermentation was 
the result of vital action. 

Later investigators have shown that both causes operate. When 
starch is taken into the mouth and mixed with the saliva excreted 
from the glands of that organ, it is thereby brought into contact with 
a ferment known as ptyalin, which at the temperature of the body 
converts the starch into sugar. 

A similar ferment is present in the growing barley grain, and if 
barley is kept warm and moist, sugar is formed. It is the same with 
other grains—the nature of the changes and substances produced being 
determined by the character of the particular ferment. 


SIZING 201 


When milk goes sour it is due to the fact that fermentation has 
taken place and has produced some acid. Pasteur showed that if milk 
is kept out of contact with air it could be preserved for months without 
turning sour. Tyndall proved that it was only necessary to “ filter ” 
the air that surrounded the milk and it could still be kept sweet. It 
was demonstrated that the necessary agent to set up milk fermentation 
was a “germ” from the air. 

The same cause explains the fermentation of sugar, but here we 
have a simple cell (yeast). And in the case of vinegar we have a similar 
organism—the Mycoderma acett. 

Spores (or seeds) from certain other plants—still low in the scale of 
- life, but higher than those already mentioned—are always present in 
air and are ever seeking a “ soil” suitable for their development and 
growth. The materials that are required by fungi for luxurious growth 
are ammonia and phosphates. 

The common name for these is mildew—the botanical, fungi ; and the 
microbiologist has identified thousands of different species. 

Then there are other bodies known as bacteria, which feed and multi- 
ply in numberless media ; and many virulent diseases are attributed to 
their action, e.g. cholera, plague, lockjaw (tetanus), yellow fever, typhoid 
fever, etc. In fact this world teems with life of all sorts, the “low ” 
type being much more plentiful and prolific than the “ higher ” forms. 

Given certain conditions, the chief of which are warmth, moisture, 
and suitable food, they will flourish and multiply at an enormous rate. 
But if they do not multiply, the most virulent of them appear to be 
harmless and even unappreciated by the ordinary senses. 

Now to apply these facts to explain fermentation and mildew as 
met with in the cotton industry. 

When flour is mixed with water and exposed to the air it rapidly 
comes into contact with certain germs, or it may contain ferments 
derived from the natural grain. These commence to convert the 
gluten which is present in the flour into small quantities of other 
chemicals, probably carbon acids, ethers, alcohols, etc. Pure starch 
will not ferment because there is no plant food in it suitable for the 
growth of germs. : 

Sizers know that flour which has been fermented for a reasonable 
time is less liable to mildew than a paste which has not been fermented. 
The explanation is that some of the substances which are the products 
of fermentation are slightly antiseptic in their nature. 

An antiseptic is a substance which by its presence prevents the 
growth of low forms of animal and vegetable life. Many substances 
are known to act in this manner, amongst which are zine chloride, 
mercuric chloride, copper sulphate, carbolic acid (phenol), iodoform, 
formalin, glycerine, etc. 


202 TEXTILE CHEMISTRY 


Mercuric chloride, or corrosive sublimate, is the most efficient, 
but so deadly poisonous in its effects on the human system that it 
must not be used for trade purposes on any account. It receives its 
application for sterilizing in typhoid fever and cholera, the virulent 
germs of which it is able to destroy thoroughly. 

Iodoform is much too expensive for general use; it is used in. 
surgery. 

Glycerine is fairly efficient if the cloth is not subjected to very 
damp conditions, but it is not suitable for heavy sizing. 

Formalin or formaldehyde is effective under certain conditions 
as a preventive of mildew, but it is much more effective against 
putrefactive bacteria. It must be remembered that this chemical is 
very volatile, and is lost by boiling. It is very effective for fumigating 
a room in which a scarlet-fever patient has been living, but to claim 
that it is equally active in the destruction of mildew spores (as was 
suggested in the celebrated “ weavers’ cough ”’ epidemic at Burnley 
a few years ago) is claiming too much for it. 

' Carbolic acid is prepared from coal tar and is purified by recrys- 
tallization. It is possible thus to obtain a very pure product. This 
quality is rather expensive for sizing purposes, but stains may result 
on the cloth with less pure grades. Carbolic is a most efficient anti- 
septic for prevention of bacterial growth, but to prevent mildew it 
must be actually in contact with the material in the solid or liquid 
condition ; its vapour is not equally effective with respect to the 
prevention of fungoid growth. Another objection to phenol is its 
characteristic odour, which is not liked in cloth. 

Copper sulphate, or blue vitriol, is a cheap and well-known 
chemical which has great power as a fungicide, in fact perhaps the best 
that is available at the present time; but for textile purposes the 
quality used in agricultural spraying mixtures is unsuitable. It is 
essential to use a grade that contains but a trace of iron salts, and it 
must also be free from uncombined sulphuric acid. 

There are other objections to its use, such as liability to produce 
copper stains, and its action as a catalyst (page 70) in the presence of 
certain other textile materials. 

Zinc chloride, first suggested by Sir W. Burnett, and consequently 
sometimes known as Burnett’s disinfecting fluid, is, generally speak- 
ing, the most satisfactory antiseptic for cotton goods. The substance 
is sometimes called ‘‘ antiseptic,’ which is not desirable, for, as we have 
already noted, this is a name used for the whole class of substances. 

Zinc chloride is deliquescent as well, and probably this property 
has had something to do with its popularity, but for heavy sizing it 
stands unrivalled at the present time. For certain goods and in special 
circumstances it is inadmissible. 


SIZING 203 


In these circumstances it is often difficult to recommend a suitable 
substitute, but salicylic acid is sometimes permissible. This is 
another very efficient fungicide, but it will change the colour of certain 
direct dyes such as Congo red, and in that event it would be better to 
use sodium salicylate, which however is, weight for weight, only about 
half as efficient. 

From this short account of antiseptics it will be seen that the 
question “ Which is it advisable to use ? ” is often by no means an easy 
one to answer. 

The action of antiseptics has not been thoroughly explained ; all that 
can be definitely stated is that they appear to be substances which are 
capable of either killing low forms of life or bringing about suspended 
animation. 

In their presence, even if all the conditions conducive to a successful 
growth are fulfilled, multiplication does not take place or is very 
considerably retarded. 

Some chemicals are more potent in this direction than others, and 
thus we find that ultimately fermented flour will mildew in spite of 
the presence of the antiseptic bodies which have been produced. 

In the case of dry starch, it is found that no fermentation takes 
place, but a starch paste will mildew. All natural starches contain 
some nitrogen compounds, and the plant probably first feeds on these ; 
later the constituents of the starch, in conjunction with the nitrogen of 
the air, form a sufficient soil. . 

The action of caustic soda as a “ preservative” (it can hardly be 
called an antiseptic) when boiled with the starch to form the paste is 
probably due to its destructive action upon nitrogenous matter, so 
reducing the available food. 

Tyndall showed conclusively that moisture was absolutely neces- 
sary to fungoid growth. A substance which is perfectly dry will never 
mildew, but add water to it even in small quantities (i.e. in the form of 
moisture), and it is liable to mildew at any time. 

Now size and sized goods always contain water. Cotton itself is 
hygroscopic, and will abstract moisture from the air, and deliquescent 
bodies like calcium and magnesium chlorides add greatly to the lia- 
bility. Therefore the greater the amount of water or deliquescent 
present in the size or on the yarn and cloth, the larger is the amount of 
antiseptic required in order to prevent the formation of mildew. 


LABORATORY EXERCISES IN THE TESTING OF “‘ RESIDUES ” 


You are provided with samples of typical ashes of various sizing in- 
gredients, etc., labelled Ato H. Examine them asinstructed below :— 
A (hard soap). Add a few drops of dilute hydrochloric acid. 
Test gas evolved for carbon dioxide. Dip a platinum wire in the liquid 


204 TEXTILE CHEMISTRY 


and test for sodium in the flame (yellow). What was the probable 
composition of the ash, and was it completely soluble in acid ? 

B (soft soap). Repeat as for A, and in addition dissolve some in 
dilute nitric acid. Concentrate and crystallize. Note shape of crys- 
tals. Are they sodium nitrate or potassium nitrate, or both ? 

C (glycerine). Extract the portion soluble in water, and test it 
for salt by adding a few drops to strong hydrochloric acid. Add dilute 
hydrochloric acid to some more and test in the flame for calcium (red). 
Also test the solution with ammonia and ammonium oxalate. What 
was the ash ? 

D (size). Extract portion soluble in water and test it for sodium 
carbonate asin A above. Extract the residue with dilute hydrochloric 
acid and test the extract for magnesium with ammonium chloride, 
ammonia and sodium phosphate (white precipitate). Test the residue 
from second extraction for clay by heating on charcoal with blowpipe, 
moistening with cobalt nitrate, and reheating (blue mass). 

KE (sago). Test solubility in dilute acids, including aqua regia. 
Fuse some with fusion mixture, lixiviate, and test solution for silica 
with hydrochloric acid (gelatinous precipitate). Also test grittiness 
between two pieces of glass. 

F (cloth). Dissolve in dilute hydrochloric acid and add am- 
monium chloride and ammonia (precipitate = aluminium). Filter, 
and to filtrate add ammonium sulphide (precipitate = zinc). Filter, and 
to filtrate add ammonium carbonate (no precipitate = absence of cal- 
cium). Then add sodium phosphate (precipitate = magnesium). 

G (clay). Test this for :— 

(a) Carbonate, with dilute hydrochloric acid. 

(6) Calcium, by flame reaction. 

(c) Bleaching powder, by mixing some with starch paste. Then 
add a little acetic acid, followed by two or three drops of potassium 
iodide. (Blue colour of iodine is liberated by chlorine evolved from 
bleaching powder.) 

H (dressing material). Extract with water and test separate 
portions for :— 

(a) Copper. Addition of ammonia produces blue colour. 

(6) Sulphate. Barium nitrate gives a white precipitate insoluble 
in nitric acid. 

(c) Magnesium. White precipitate with ammonium chloride, 
ammonia, and sodium phosphate. 

Test the well-washed residue from the water extraction for barium 
in the flame, after moistening with hydrochloric acid. 


SECTION XVI 
THE PROCESS OF BLEACHING 


HE Nature of Colour. Colour is a physiological sensation 
produced by the phenomenon known as light. 


Light is a form of energy, the most important source for 
the production of which, so far as this universe is concerned, is 
the sun. Other sources are often called artificial. 

From the sun, ninety-two million miles distant, the energy is 
radiated by vibration of a medium that appears to be unappreciated 


Violet 


by our senses, the rate of travelling being about 186,000 miles per 
second ; that is, the time of passage is about eight minutes. 

It is now more than 250 years since Sir I. Newton showed, by 
placing a glass prism in the path of the sun’s rays, that a band of colours 
could be obtained therefrom (Fig. 233). This demonstration is usually 
referred to as “the Newtonian Experiment to show the composite 
nature of white light.” 

The explanation of this phenomenon is that as the rays of light pass 
through glass they are not all bent or refracted to the same extent, and. 
thus on emergence they are more or less sorted out. The red rays are 
refracted least, and violet rays most ; and between these two extremes 
occur yellow, green, and blue. This power of being able to resolve a 
composite light is not limited to glass nor to the phenomena of refrac- 
tion through glass. 

All substances do three things to rays of light: (1) Absorb them, 
(2) transmit them, (3) reflect them. If a substance absorbs all, or 
nearly all, the rays that fall upon it, it is said to be black ; those bodies 
which absorb very few and reflect nearly all are termed. white. 


205 


206 TEXTILE CHEMISTRY 


Other substances absorb some and reflect others, and as our optic 
nerve (by means of which we see) only conveys to our brain the 
sensation produced by those rays which actually irritate it, that 
is, the rays which are reflected from the substance, our perception 
of colour will depend very largely upon the nature of the reflected 
rays. 

Bodies vary much in the power of selective absorption (and conse- 
quent reflection), as can be demonstrated by many interesting experi- 
ments, e.g. if a bunch of flowers be illuminated with white light the 
individual flowers will absorb certain rays and reflect others, and the 
kind reflected will in all probability differ in each case, and thus we 
say the flowers are of different colours. But if the light falling upon 
them be of one wave-length only, that is, of one colour, a different 
effect is produced. 

Suppose the illuminating source is produced by holding crystals of 
common salt in a bunsen flame. This radiates chiefly what is termed 
yellow light, and thus only the yellow flowers appear in their usual 
colour, and the rest will appear to be black, the depth of shade depend- 
ing upon the thoroughness of absorption. 

But if the bunch be illuminated with the light from burning mag- 
nesium—a very white light, and.one particularly rich in blue and 
violet rays—the individual flowers appear in their usual colours, and 
probably brighter, and showing differences in tint much better than 
in ordinary daylight. 

This explains why materials appear to give different shades and 
colours in daylight, electric light, gas light, etc. 

White substances reflect back the light they receive practically 
unchanged. 

Now in bleaching the intention is to so alter the surface of the 
material that it shall reflect back as much white light as possible. 

To some extent this is done by exposure to sunlight itself, and also 
by polishing the surface, but to produce a dead white the particles at 
the surface which show a selective absorption or reflecting capacity 
must be removed altogether, or altered until they will reflect the 
incident light practically unchanged. 

That is the rationale of bleaching. 

Bleaching is a chemical process entirely, and in many cases one of 
oxidation (Section VII, page 63). Many chemicals are capable of 
changing the constitution of natural and other substances by oxida- 
tion, but the same chemical is not always so efficient with different 
substances, and in other cases certain destructive chemical action may 
result. 

Therefore many substances are in use. They are known as bleach- 
ing agents. 


BLEACHING 207 


Chlorine (the preparation and properties of which have been con- 
sidered in Section XI, pages 125-130) is the chief bleaching agent in use 
for cotton. Owing to technical difficulties the gas is not applied directly, 
put as some compound which is capable of yielding it, such as bleaching 
powder or sodium hypochlorite. Water must be present also. 

The explanation of the reaction is that chlorine decomposes water, 
liberating oxygen in the nascent or atomic condition. The oxygen 
then oxidizes the natural colouring matter. 


Nearly all natural substances when oxidized become white, Le. 
the new compound produced reflects back more light than its prede- 
cessor. This may be illustrated by passing a stream of chlorine 
through a dilute solution of a dye. 

With bleaching powder an acid must be added to liberate chlorine. 
This is one reason for souring the goods. Any acid will do, even 
carbonic, produced from the carbon dioxide in air to which it is ex- 
posed. On a small scale acetic is the safest to use, but the bleacher 
uses sulphuric or hydrochloric. 

Sodium hypochlorite acts in a similar way, even without acid, but 
the addition of the latter promotes the action. 

Sulphur dioxide (for preparation and properties of which see 
Section XI, pages 132-133) is not used for cotton, but is chiefly used 
for bleaching straw, wool, etc. 

It is considered that the nature of the chemical reaction is here 
different from that with chlorine. In some cases the sulphur dioxide 
itself combines with the coloured body, and in others it decomposes 
the water which is present, liberating hydrogen, which in its turn 
reduces the coloured body. , 

Articles (particularly wool) bleached with sulphur dioxide are not 
- permanently decolorized. When washed with soap or exposed to air, 
the colour returns, owing to re-oxidation. 

In order that the bleaching operation may be a success it is neces- 
sary that the chemical shall come into intimate contact with the 
material, hence the necessity for removal of all grease and dirt, which 
is done by use of chemicals known as detergents. Those generally 
used are sodium carbonate or soda ash, caustic soda, lime, soap, resin, 
etc., for cotton, and ammonium salts for wool. 

Textile materials may be and are bleached at all stages of manufac- 
ture, but the most important application is to cotton cloth. 

In this process there are five distinct operations :— 

1. Singeing and washing if necessary. 

2. Removal of sizing materials and impurities in the cotton by 

(a) Boiling with lime under pressure. 


208 TEXTILE CHEMISTRY 


(6) Acidifying to decompose lime soaps. 
(c) Boiling with resin soap if a “ madder” bleach is required. 
(zd) Boiling with soda ash under pressure. 
(e) Washing. 
3. Treatment with bleaching powder, termed “ Chemicking.” 
4. Souring or treatment with weak acid, to remove the lime and 
liberate the rest of the chlorine from the bleaching powder. 
5. Final washing and drying. 
Singeing is done to remove all loose fibre from the face of the cloth, 
and is performed by rapidly passing the fabric over a hot plate or 
through a flame from a,series of bunsen burners. Sometimes the pro- 


SINGEING  sesure 
APPARATUS RS 
S eas Cl ot h 


Fig 258 


cess is repeated, and sometimes, if a very smooth finish is required, it 
is carried out a third time (Fig. 238). 

Washing is done in special machines in which the cloth is subjected 
to the action of wooden beaters, and as a rule the wet material is 
allowed to stand piled up for some hours after washing, in order that 
the starch may start fermenting, which assists in its subsequent 
removal... 

Boiling with lime or alkali is done in large iron vessels called kiers, 
the process being termed bowking. 

Kiers vary considerably in size and design, but Fig. 234 may be 
considered to represent the type in most general use. 

The bottom A is filled with smooth stones to provide drainage. On 
the top is packed the cloth B. Steam is allowed to enter the U-shaped 


BLEACHING 209 


pipe at C. Near the bottom it passes an injector pipe D, which is fed 
from the bottom of the kier. Therefore as the steam rushes up branch 
E it carries with it the liquid from the kier, and as it empties itself in 
the form of a spray, establishes a circulation in the kier. 

Pipe G is for running off the liquor at the end of the boil. A safety 
valve, pipes for filling the vessel with water or alkali, and a man-hole 
are also fixed in the top of the kier. 

They are made to hold any amount of cloth up to two tons, and in 
exceptional cases more than 


that. They are often ten to Water —> 


twelve feet in height and four site alve 
to six feet in width. Manhole el ‘ <— 
A lime boil needs from six CANI\WS =C 


to twenty-four hours, according 


to the quantity of cloth being 

treated. = 
The resin soap and lye boils = 

are extended over three or B 

four hours. Washing, chem- 


icking, and souring of the 
bowked cloth is carried out in 
a machine such as is shown in 


Fig. 235. O 

The cloth is passed in rope WAC A 
form between squeezing rollers, 
and, guided by means of wooden 
pegs, it passes round a roller in G Fig23+ 
the bottom of the box which 
contains the acid or bleaching solution. If it is being washed the water 
is sprayed on to it just before it enters the box. 

The strength of acid used is such that it stands at 3° to 4° Tw., 
i.e. a sp. gr. of 1-015 to 1-02. 

Bleaching-powder solution has to be very carefully prepared to 
ensure the absence of lumps, which would produce oxy-cellulose, and 
so tender the cloth. The strength generally used is about 3° Tw. 

During the last few years considerable headway has been made 
with the process known as electric bleach, in which sodium hypo- 
chlorite is prepared electrolytically from common salt, and the solution 
so obtained is used instead of bleaching powder. Several forms of 
apparatus are on the market for making the bleach liquor, the essential 
point in their construction being that the liquid shall be thoroughly 
agitated during the decomposition, and its temperature kept from 
rising above 30°C. Under these conditions solutions of sodium 
chloride of various degrees of concentration can be electrolyzed by 


14 


D 


210 TEXTILE CHEMISTRY 


currents of suitable strength, and the liberated ions caused to combine 
in the solution instead of escaping from it. 

In the Oetell electrolyzer, illustrated in Fig. 236, this is effected by 
using plates of gas carbon placed close together, the liquid being circu- 
lated by the liberated bubbles of hydrogen, which cause it to rise and 
flow over the glass partitions, from which it again finds its way to the 
bottom of the cell. 

The production of this “ electric bleach liquor ” can be well illus- 
trated with the apparatus shown in Fig. 237. The large boiling-tube 
B (about 2 inches in diameter) is closed with a rubber bung through 
which pass two carbon pencils C which are connected to the poles of a 


secondary battery giving a voltage of between 6 and 8 volts. Besides 
these the stopper holds a dropping funnel A, the end of which reaches 
to the bottom of the vessel B, a piece of glass tubing D, which also goes 
to the bottom, and a delivery tube E which passes to the bottom of a 
reservoir EF, and which can be closed by means of a tap G. 

To use the apparatus to prepare sodium hypochlorite, put a solu- 
tion of common salt in A, open both taps, and allow it to flow into B. 
When the vessel is about half full close both taps, and pass the electric 
current. Gas is liberated from both rods, in one case to a much greater 
extent than the other, and as it collects above the surface of the liquid 


BLEACHING 211 


in B and is unable to escape, the liquid is gradually forced up tube D 
into vessel A again. 

The action of the current causes a partial destruction of the carbon 
rods and therefore it is advisable to introduce a filtering arrangement 
at the top if a clear liquid is desired. 

At intervals the liquid may be passed back again into B and the 
gas collected in a test tube from E and proved to be hydrogen by the 
usual tests for that gas. 


OUTLINE DIAGRAM 

OETELL ELECTROLYSER 

‘To Dynamo Fig.230 
carbons eae 
DD sont circulation 


Sol? fate 
Inney { 


1 Vessel. 


Hole 


| _| glass 
“ie tt, hy PSs HS CEE | P 5 


Hole Salt Solution 
; * Cuter Vebsel) 


It is claimed for this bleaching liquid that it is not more costly than 
bleaching powder, that it is more efficient, and less liable to tender the 
goods, and also that it produces much less troublesome waste, and in 
particular no lime by-products. 

Whether the above claims be fully substantiated or not, there is 
no doubt but that it enables bleaching to be carried on much more 
efficiently on the small commercial scale, particularly in laundries and 
small mills where the manufacturer does his own bleaching and dyeing. 


212 TEXTILE CHEMISTRY 


Mather & Platt, who also make an electrolyzer in which the circu- 
lation is effected by using a small pump, state that the electric pressure 


: 1 | csi Hydrogen 


Fig 237 


generally convenient is 100 to 110 volts, and their standard electro- 
lyzer is made for this electromotive force, ‘Two cells can be placed in 
series if the pressure available is 200-220 volts. 


BLEACHING 213 


The current required for a full output of the standard-size cell is 
80-100 amperes. 

It may be somewhat interesting to know that the preparation sold 
under the name of “ Milton” is sodium hypochlorite made in this 
manner. 

The chemistry of the process may be represented as 

(a) Decomposition of salt into sodium and chlorine. 

(b) Decomposition of water by the sodium with production of 
caustic soda and hydrogen. , 

(c) Reaction of chlorine with caustic soda to produce sodium 
hypochlorite and hydrogen. 

At the same time small quantities of other compounds are pro- 
duced. 


SECTION XVII 
DYEING 
aE HE chief methods adopted for dyeing cotton yarn on an 


experimental scale with :— 
(a) direct, (b) basic, (c) sulphur dye-stuffs, (d) mineral 
colours. 
Dyeing is the art of producing a colour (or change of colour) on 
fibres, cloths, fabrics, and other articles. 


SUBSTANCES THAT HAVE BEEN AND ARE USED FOR DYEING 


Until about sixty years ago (1856) the substances used were natural 
dye-stuffis obtained either from plants and animals such as woad, 
indigo, cochineal, madder, cutch, logwood, turmeric, annatto; or 
certain chemicals (minerals) such as iron, lead, and manganese salts. 

Some of these are still used, but since 1856 the number and variety 
of dye-stuffs have been enormously extended by the preparation of the 
aniline and other dyes from coal tar, thousands of which are now on 
the market. | 

Alizarine (the dye-stuff in madder) is now prepared entirely from 
the same source, and indigo is largely so manufactured. Of the old 
natural dye-stuffs practically only two remain—logwood and cutch. 

Can all fibres be dyed with all these thousands of dye-stuffs ? 
They cannot; there is considerable variation in this respect. . 

As a rule animal fibres (like wool and silk) have a much greater 
affinity for dyes than vegetable fibres (like cotton), and therefore we 
find that similar treatment or identical dye-stuffs will not produce 
identical results in cloths made from mixed fibres. 

Again, it is found that to produce permanent and good colours 
many processes, and the application of several chemicals, are some- 
times needed, e.g. Turkey red used to take months to produce, and 
even now it requires days. 

Hence dye-stuffs have been divided into classes, largely governed 
by the method of dyeing that is possible with them ; and of these, the 
class in which there is the largest number at the present time is that 
known as 

‘‘ The Directs,”’ \ 


214 


DYEING 215 


This name was given because the colour could be applied direct 
to the cotton fibre without first treating it with a fixing chemical. 

The first Operation in Dyeing. The first step is always preparation 
of fibre or fabric. Dye liquor must penetrate the fibre in order to 
produce a permanent or level result. ‘Therefore all fat and filling, and 
injurious substances, must be removed, and if the colour desired is a 
light shade, the natural colour of the yarn must be removed by 
bleaching. 

To get rid of the fat and the grease cotton is boiled in a solution of 
very dilute caustic soda, or a 1 per cent. solution of soda ash for some 
time, and afterwards well rinsed in clean hot water. This is called 
** boiling out.” 

Application of Dye-stuff to Cotton Fibre. It is applied in solution. 
Many dye-stuffs are soluble in water, others in water containing a few 
drops of acetic acid or a few grains of sodium carbonate. Some 
require the presence of a caustic alkali, and others a chemical called 
sodium sulphide. 

Ordinary direct cotton colours are usually dissolved in water, with 
the addition of a little sodium carbonate or sodium phosphate to make 
the solution more perfect. 

To determine the Quantity of Dye-stuff to use :— 

First select on a pattern card (which is the result of experimental 
dyeing by the dye-maker) the shade desired. 

This will give (1) Percentage of dye-stuff required ; (2) percentage 
of assistants, as the chemicals are called which are used in the dye bath. 

This percentage refers to the weight of the material to be dyed ; 
therefore the next step is to weigh the cotton in the dry condition, and 
then to calculate the weight of dye-stuff and chemicals to be dissolved 
in the bath. 

Suppose the pattern card said 2-5 per cent. dye, 20 per cent. 
- Glauber salt, 1-5 per cent. soda ash, and the material to be dyed was a 
10-gram hank, the required quantities would be dye 0-25 gram, 
Glauber 2 grams, soda ash 0°15 gram. 

For experimental dyeing, as the quantities required are so small, 
it is usual to make up standard solutions, i.e. solutions of definite volume 
containing a known weight of dye; e.g. 1 gram of dye in 100 c.c. of 
water: then 10c.c. will contain 0-1 gram, and if 25 c.c. of this solution 
be used we should get 0-25 gram without directly weighing this small 
quantity. 

The Volume of the Dye Bath. As the quantity of liquor will affect 
the strength of the solution, and the strength of the solution will 
materially affect the shade and other features of the dyed goods, the 
~ volume of the dye bath is a very important factor. 

For hand-dyed yarn it is usual to keep the ratio between 1:12 


216 TEXTILE CHEMISTRY 


and 1: 20—different makers vary slightly. Assume our instructions 
are 1:15. 

This means that if the goods weigh 1 gram the volume of the bath 
should be 15 c.c., or, for 10 grams, a volume of 150 c.c. So after adding 
the dye and assistants to the dye pot, the total volume is made up to 
150 c.c. and stirred. 

The Temperature at which it is desirable to carry on the Dyeing 
Operation. The most successful dyeing is obtained by entering the 
goods when the bath is warm (say at 60° C.), then gradually raising to 
the boil, and keeping at the boil for about thirty minutes. If the bath 
is too hot when the yarn is entered, the colour “rushes on” and 
produces uneven dyeing. 

How the Goods should be entered, and other Precautions and Manipula- 
tions that are necessary during the Process. The hanks should be put 
into the bath in a uniformly wetted condition, but not running with 
cold water (‘‘ wetted out ’’). They should be wrung well, shaken out 
to ensure even wetting, and immersed as quickly and completely as 
possible. They should be turned all the time they are dyeing, to ensure 
evenness and to keep the bath at a uniform temperature. 

The water used must not be hard (particularly with magnesium 
salts) or uneven dyeing will result. 

Reasons for adding the various Assistants to the Bath. Sodium 
carbonate is added to ensure complete solution and to make an alkaline 
bath, which is necessary when dyeing cotton with direct colours. 

Glauber salt (sodium sulphate) is to render the dye-stuff less soluble, 
in other words, to throw the dye out of solution, so that more is taken 
up by the fibre. As it is, these baths are never exhausted, seldom more 
than one-third of the dye being abstracted. Common salt is used 
for a similar reason ; it is cheaper than Glauber, but not quite so good 
for light shades. Sodium phosphate is better than either, but it is 
much more expensive. 

The Manipulations necessary after Removal of Yarn from the Dye 
Bath. Directly the yarn is removed from the bath it should be well 
washed in running cold water until all loose dye liquor is removed, well 
wrung, and dried in the air. Sometimes it is soaped after washing, i.e. 
it is worked for ten minutes in a dilute solution of pure soap and water 
at a temperature of 40°-60°C., and then dried without rewashing. 
This brightens the colour and increases its fastness somewhat. 

‘¢ Basic Dyes.”’ As a rule, for brilliancy of shade, the direct dyes 
are much inferior to another class called the basics—so named because 
they react with certain acids in a very similar manner to basic radicles, 
to form colour salts. | ; 

The earliest discovered of these were mauvine and fuchsine. 
Others are methyl violet and methylene blue. Because of the great — 


DYEING 217 


intensity of the colouring principle, very little dye-stuff is required for 
a large quantity of goods. 

They have not nearly so large an application as directs, chiefly for 
two reasons :— | 

1. They are much more fugitive to light and washing. 

2. For vegetable fibres they cannot be dyed in one operation. 
(For animal fibres they can.) The fibre must be mordanted with 
certain chemicals in order that the colour shall not wash out. 

Mordanting. A mordant is a substance which is capable of being 
absorbed by a fibre, and which, when brought into contact with a 
dye-stuff, forms a compound with it in the interstices of the fibre, and 
thus prevents its easy removal by washing. 

This compound is usually called a “Jake.” Substances which are 
capable of acting as mordants to cotton are :— 

(a) A solution of albumen or white of an egg in cold water, fixed 
by passage of the impregnated yarn through hot water. 

(b) Tannic acid. 

(c) Turkey red oil. 

(dq) The direct cotton colours. 

The cotton yarn is well worked in these, but if tannic acid is used 
another process is necessary to fix it on the fibre before putting it into a 
dye bath. 

Several substances can be used for this purpose: the two in general 
use are (a) tartar emetic; (6) ferrous sulphate. — 

The iron salt is used only for dark shades. 

Mordanting and Fixing. The process is carried out in this way: 
The boiled out yarn is put in a bath of cold tannic acid, boiled up, 
and then allowed to cool down or “ feed ” in it for some hours—say 
all night. 

After removal the yarn is squeezed uniformly and put into the cold 
fixing bath for an hour or more. Of course the yarn is turned at 
intervals during the immersion. After removal from the fixing-bath 
it is squeezed and rinsed, when it is ready for the dye bath. 

Quantities of Mordant and Fixer to be used. Tannic acid, from 
0-5 per cent. for light up to 8 per cent. for dark shades ; tartar emetic, 
from 0-25 per cent. for light up to 4 per cent. for dark shades. 

Preparation of Dye Bath. The method is similar to that described 
for directs, the calculation for quantities required being identical. 
The bath is generally made not quite so “ short ”—20 of liquor to 1 of 
goods being usual—and no soda ash or Glauber salt is added, but as a 
rule a little dilute acetic acid is advisable. 

The temperature when the yarn is entered should not exceed 
40° C., and it may be colder with advantage. If higher, the colour 
tends to rush on and uneven dyeing is the result, 


218 TEXTILE CHEMISTRY 


The bath is then raised very gradually nearly to the boil, and kept 
so until the total time of immersion has amounted to half an hour. 
Washing and soaping follow as with directs. 

Precautions in Dyeing Basics. To obtain really good results in 
dyeing basic colours, several precautions are necessary. One of the 
most important is the necessity for pure water. Hardening salts 
produce uneven dyeing much more readily than with directs, due to 
precipitation of the colour. Peaty matter and the slightest trace of 
iron salts also spoil the shade. 


LABORATORY EXERCISES IN THE DYEING oF CoTTON YARN WITH DIRECT 
AND Basic COLOURS 


The method which I have found to be most satisfactory for initiating 
elementary students of textile chemistry into the art of practical 


Fig. 230 


dyeing is to provide them with standard solutions of dye-stuffs and 


chemicals and the following set of instructions. 

“Ten-gram ”’ hanks, bleached and unbleached, are also available. 
At Nelson, where they were purchased ready for use, two-fold 20’s 
and two-fold 40’s soft spun yarn was dyed. At this College we are 
supplied from our own spinning department, and as a rule single-twist 
is used. A little more care is necessary in the dye bath on this account. 

The dyeing is done in porcelain beakers of at least 300 c.c. capacity, 
which are suspended from removable copper lids in sets of four. They 
are surrounded with water in a copper vat, which is heated by and 


a 4 


DYEING 219 


stands upon a ring or Argand gas burner standing on a sheet of asbestos 
placed on an iron grid to protect the bench (Fig. 239). 

Dyeing-sticks made of }-inch glass rod are used. Some of these 
are bent at 45° to permit the complete immersion of the yarn while in 
the liquor. 

Each student is expected to dye light and dark shades of at least 
two direct and two basic colours, to take them down to the weaving- 
shed after they have been dried and inspected, to wind them on pirns 
and weave them up as weft for a good weft face cloth. 

Part of the woven sample is retained by the student and part by 
the College. 


COPY OF INSTRUCTIONS GIVEN 
Instructions for Dyeing Direct Cotton Colours 
You are provided with the following :— 
Four 10-gram bleached hanks for light shades. 
Four 10-gram unbleached hanks for dark shades. 
Standard solutions of these dyes :— 
Direct yellow C 
Direct green B of a strength that 10 c.c. contains 
Trisulphon violet B 0-05 gram. 
Chloramine sky-blue FF 
Also : 
Soda ash solution for boiling out yarn (1 per cent. strength). 
Soda ash standard solution, 10 c.c. containing 0-075 gram. 
Common salt ,, i‘ 10 c.c. * 2-5 a 
Glauber salt _,, - 10 c.c. - 1:0 eo 


I. Boil out the unbleached yarn in the 1 per cent. solution of soda 
for half an hour. Rinse well in hot and then cold water until all 
chemical is removed. Squeeze well and shake out. 

Soak the bleached yarn in hot water,then in cold, squeeze and shake. 

II. Prepare the following dye baths, and work them four at a time, 
two workers to the set, so that each student has two hanks to turn 
and dye. 

(a) For light shade (1 per cent.) Chloramine sky-blue FF. 

20 c.c. of dye solution (i.e. ‘1 gram). 
10 c.c. of Glauber solution (i.e. 1 gram or 10 per cent.). 
10 c.c. of soda ash solution (i.e. 075 gram or -75 per cent.) 
150 c.c. of water. 
(b) For dark shade (4 per cent.) same colour. 
80 c.c. of dye solution (i.e. -4 gram). 
10 c.c. of salt solution (i.e. 2:5 grams or 25 per cent.). 
10 c.c. of soda ash solution. 
90 c.c. of water. 


220 TEXTILE CHEMISTRY 


(c) For light shade (-5 per cent.) Direct green B. 
10 c.c. of dye solution (i.e. -05 gram). 
10 c.c. of Glauber solution (i.e. 10 per cent.). 
10 c.c. of soda ash solution (i.e. *75 per cent.). 
160 c.c. of water. 
(d) For dark shade (3 per cent.) same colour. 
60 c.c. of dye solution (i.e. -3 gram). 
10 c.c. of salt solution. 
10 c.c. of soda ash solution. 
110 c.c. of water. 
(e) For light shade (-5 per cent.) Direct yellow C. 
10 c.c. of dye solution (i.e. -05 gram). 
10 c.c. of Glauber solution. 
10 c.c. of soda ash solution. 
160 c.c. of water. 
(f) For dark shade (2 per cent.) same colour. 
40 c.c. of dye solution (i.e. -2 gram). 
10 c.c. of salt solution. 
10 c.c. of soda ash solution. 
130 c.c. of water. 
(g) For light shade T'risulphon violet B (-25 per cent.). 
5 c.c. of dye solution (i.e. -025 gram). 
10 c.c. of Glauber solution. 
10 c.c. of soda ash solution. 
165 c.c. of water. 
(h) For dark shade (2 per cent.) same colour. 
, 40c.c. of dye solution (i.e. -2 gram). 
10 c.c. of Glauber solution. 
10 c.c. of soda ash solution. 
130 c.c. of water. 


III. Raise the dye bath to 50° C., stirring at intervals. Take the 
bent glass rod in the left hand and a straight one in the right. Hang 
the hank on the bent rod, hold it vertically over the dye pot, and then 
drop it down so that the bottom of the hank enters first, and the 
bent rod last of all. Use the straight rod to help to immerse it com- 
pletely. Atintervals lift up the bent rod so that about a quarter of the 
hank is held out of the dye liquor, and then, by passing the straight 
rod under it, turn the hank ; i.e. lift up a portion in the air and move 
it to the other side of the bent rod. Repeat with the fresh portion 
which has come up out of the pot—the passage of the hank being 
similar to that of an endless rope over a pulley. 

Continue dyeing at the boil for half an hour. 

IV. Remove, wash under the tap or in a vessel containing plenty 
of cold water, and put into a soap bath at 60°C. for ten minutes. 


DYEING 221 


Squeeze, but do not wash again. Shake out well and hang over a 
glass rod to dry in the air. Label each hank with your name and 
particulars of colour and percentage of dye used. 


Instructions for Dyeing Basic Colours on Cotton 


The porcelain trough labelled “ A” contains thirty 10-gram hanks 
of cotton yarn that have been “feeding” for about 12 hours in a 
solution of tannic acid containing 6 grams in 2,000 c.c. of water at 40°C. 

These are to be used for light shades. 

The trough labelled ‘“‘ B ” contains the same number which have 
been steeping in a solution of double the strength, i.e. 12 grams of 
tannic acid in 2,000 c.c. of water. 

These hanks are to be used for dark shades. 

Proceed to FIx your own hanks in the correct solution of tartar 
emetic which is provided. 

Solution “‘C” contains 1-5 gram of tartar emetic per 1,000 c.c. 

This is for fixing hanks from “A ”’ for light shades. 

Solution “‘D” contains 3 grams per 1,000 c.c. and is for hanks 
from ‘“B” for dark shades. 

Take out three hanks for each shade, gently squeeze them, shake 
out, and put each set into 200 c.c. of the correct fixing solution in a 
porcelain pot and work in the cold for 15 minutes. Remove, squeeze, 
and rinse with water slightly. | 

Work in a slightly warm soap bath for two or three minutes, wring 
out, and rinse well. They are now ready for the dye bath. [This step 
may be omitted if time is limited. ] 

While the hanks have been fixing the dye bath should be prepared, 

1. In a porcelain pot put 100 c.c. of cold water. 

2. Add 2 c.c. of a 10 per cent. solution of acetic acid. 

3. Enter the yarn and turn it two or three times. 

4. Remove the yarn for a few seconds. 

5. Add the dye solution (for quantities required see below), stir 
well, and add sufficient water to make the total volume of the bath 
200 c.c. 

6. Re-enter the yarn and work in the cold bath for 10 minutes, . 
then slowly raise the temperature to 60°C. Work the yarn all the 
time, and when it has been in for about 45 minutes in all, remove it. 

7. Wash in cold water, soap in just warm soap bath, squeeze, shake 
out, and dry as before. 

Quantities of dye solution required for dyeing one 10-gram hank :— 


Bismark brown, light shade 0-75 per cent.,i.e. 15 c.c. of solution 
Do. Bete yj) o Fe = 60 Re ‘A 

Brilliant green, light __,, 0-5 4 5 os WLU eae 4 
Do. dark 29 2 9 oe) 40 29 99 


222 TEXTILE CHEMISTRY 


Methyl violet, light shade 0-25 per cent., i.e. 5 c.c. of solution 


Do. dark 99 1 29 29 20 ” 99 
Methylene blue, light sya eae yr Bee an 
Do. dark 2 99 > 40 be) 99 


All the above standard solutions were made up by dissolving 5 
grams of dye-stuff in 1 litre of water to which a few drops of acetic acid 
had been added previously. 

The Sulphur or Sulphide Colours 

The sulphur or sulphide colours form a class of direct cotton dyes 
which are | 

(1) Insoluble in water, but soluble in sodium sulphide. 

(2) Oxidizable in air. 

(3) Very fast to light, washing, milling, alkalis, acids, cross-dyeing, 
and stoving (sulphur dioxide). 

(4) Not very resistant to chlorine. 

In trade they are known under other names, e.g. thion, katigen, 
thionol, cross dye, immedial, kyrogene, thiogene, etc. 

They are rapidly displacing aniline blacks, indigo, catechu browns, 
khaki, logwood blacks, etc. They form excellent bottoms for basics 
and indigo. 

For experimental dyeing it is not advisable to prepare standard 
solutions. A larger amount of dye-stuff is required to produce the 
corresponding depth of shade than is the case with directs or basics. 
From 1 per cent. to 4 per cent. for light shades, and 8 per cent. to 12 
per cent., or even 15 per cent., for dark shades, is required. 

The dye solution is prepared by mixing the indicated quantities of 
dye-stuff, sodium sulphide, and soda ash with boiling water till all is 
dissolved. The amount of sodium sulphide required varies with the 
make and brand of dye, and whether the sulphide used is calculated 
as concentrated or crystallized. 

1 gram of conc. sod. sulphide = 2 grams of the cryst. variety. 

Single brands of colour usually require half their weight of sodium 
sulphide (conc.), and extra brands an equal amount. 

The addition of Glauber salt to the dye bath (if required) is made 
after the colour has been dissolved. Then add the rest of the water 
(at boiling temperature) to make a volume of 20 to 1 of the cotton. 

Soda ash used is from 4 per cent. to 10 per cent., Glauber from 20 
per cent. to 30 per cent. (or salt 15 per cent. to 25 per cent.). Some- 
times 2 per cent. of Turkey red oil is added to the bath. 

Dyeing Cotton with Sulphur Colours. For most colours, the yarn 
should be entered at the boil and the source of heat immediately with- 
drawn. Light blues are best dyed at 30° to 40° C., dark blues at 50° to 
70° C., mercerized yarn at 70° to 80° C., and some can be dyed in the 
cold, but in this case the bath should be more concentrated. 


DYEING 223 


The dyeing should last # hour to 1 hour, and the hanks should be 
turned every few minutes. While so doing they should not be exposed 
to the air, but kept under the surface of the liquid. 

If the cotton is mercerized, more sodium sulphide is needed, and 
no common salt should be used. 

When dyeing is finished the yarn should be removed quickly, 
thoroughly squeezed, quickly rinsed (to prevent unequal development), 
well shaken in the air, and soaped. 

As exercises dye 10-gram hanks of cotton as follows :— 

(1) 5 per cent. sulphur blue. 

(2) 10 per cent. do. 

(3) 1 per cent. sulphur black. 

(4) 10 per cent. do. 


: 3 per cent. sod. sulphide (conc.). 
Using for (1) 9 P 7 are te ( ) 


and (3) 10 2 Glauber salt. 
10 - sod. sulphide (conc.). 
Using for (2) et 
and (4) 60 < Glauber salt. 


The Mineral Colours. In spite of the fact that the “coal tar 
dyes ” have obtained such prominence in the industry, the use of cer- 
tain mineral colours is by no means extinct, and it is doubtful if they 
will ever be completely driven off the market for certain classes of trade. 

The chemistry of the process should be first studied by perform- 
ing the following experiments :— 

1. Prepare the following solutions :— 

(a) Lead acetate, by dissolving a few crystals of “sugar of 
lead ” in water. 

(b) Potassium dichromate in water. 

(c) Manganous chloride, by acting on manganese dioxide with 
strong hydrochloric acid, filtering and boiling till excess 
of chlorine is expelled. 

(d) Ferrous sulphate and ferric chloride. 

(ec) Potassium ferrocyanide—use yellow prussiate of potash. 

2. To lead acetate solution add some potassium chromate solution. 
Note the formation of a yellow precipitate of lead chromate (chrome 
yellow). Divide this precipitate into three portions, to :— 

(a) Add nitric acid and note that it dissolves. 

(6) Add a little boiling lime water. Note change of colour to 
chrome orange. - 

(c) Add excess of caustic soda and that note it dissolves. 

3. To a little of the manganous chloride solution add two or three 
drops of caustic soda. Note the formation of a white precipitate, 
which rapidly darkens on addition of more soda or on boiling. 


224 TEXTILE CHEMISTRY 


Divide the precipitate into three parts, and to 
(a) Add a little bleaching-powder solution—note increased 
darkening (manganese bronze) ; 
(6) Add some potassium dichromate solution and note a 
similar result ; 
(c) Add sodium hypochlorite solution and note what happens. 
4. To separate portions of ferrous sulphate solution add :— 
(a) Caustic soda; (b) sodium carbonate solution. 
To each add some bleaching-powder solution. Note formation of 
iron buff. 
Repeat the experiments with ferric chloride solution. 
5. Mix ferrous sulphate and ferric chloride solutions, and then add 
potassium ferrocyanide. Note production of Prussian blue. 


Dygrina MINERAL COLOURS 


1. Chrome Yellow. 

Prepare a solution of basic lead acetate by mixing 12 grams of 
commercial sugar of lead, 6 grams of litharge, 35 c.c. of water. 

Stir up at intervals for five or six hours. Dilute with water till its 
sp. gr. is 1:05 (10° Tw.). Allow it to settle or filter. 

Work the previously boiled-out yarn in this for half an hour. 
Wring well, shake, and put it into a bath of potassium dichromate 
solution containing 8 grams per litre. 

Remove, wash thoroughly, treat with a weak solution of Turkey red 
oil in water and dry. 

2. Chrome Orange. 

Treat hanks that have been dyed chrome yellow (but which have not 
been oiled) rapidly in a bath of clear boiling lime water. Turn very 
rapidly two or three times, remove as soon as the colour is fully 
developed, and rinse twice. 

Enter in a warm bath containing soap, a little soda ash, and cotton- 
seed oil. 

Squeeze and dry without further rinsing. 

3. Iron Buff. 

Evenly impregnate the yarn with a solution of ferrous sulphate, 
squeeze, and pass it through a weak solution of caustic.soda or soda 
ash or lime water. 

Then pass it through a weak solution of bleaching powder. Rinse 
and dry. 

To produce a much brighter and better shade of iron buff :— 

Use a solution of “nitrate of iron” of from 2° to 6° Tw. 

Nitrate of iron is prepared from ferrous sulphate as follows :— 

Take 340 grams of ferrous sulphate, dissolve it in water, add 20 c.c. 


s 


conc. sulphuric acid and 20 c.c. of conc. nitric acid. Boil for some _ 


DYEING 225 


time, keeping the volume constant. Filter: a dark red liquid is 
produced. Dilute it till correct sp. gr. is obtained. 
4. Prussian Blue. 
_ Dye the cotton iron buff and then pass it through a solution of 
potassium ferrocyanide acidified with sulphuric acid. 
5. Manganese Bronze. 
Impregnate the yarn with a solution of manganous chloride. Fix 
it in a hot solution of caustic soda containing 30 grams per litre. 
Rinse it in a weak solution of bleaching powder (strength 1° Tw.). ° 
Wash and dry. 


TESTING DyED SAMPLES 


It is very essential that every dyed sample should be submitted to 
certain tests, and that a systematic record of the same should be pre- 
served. The plan illustrated on the next page will be found a suitable 
one for beginners. 

To carry out the tests proceed as follows :— 

1. Fastness to Light. Take a piece of glass about 4 inches by 6, and 
cut a piece of white cardboard the same size. Bind them together 
along one edge by means of a strip of photographic adhesive “ leather- 
ette.”’ On the top of the cardboard put a piece of black paper, on the 
top of this a piece of white filter paper, and on the top of this a few 
strands of the dyed yarn which is to be tested. 

Cover half of it with two thicknesses of black paper and let the glass 
fall into position. 

The remaining three edges can now be bound, or two rubber bands 
can be passed round. 

The whole arrangement can now be exposed to bright direct sun- 
light for days, or weeks (if necessary). 

The degree of fastness is judged by comparing the portion exposed 
with the portion that was kept under the black paper. 

Generally speaking, sulphur and mineral dyes are fast to light ; 
basics very fugitive (particularly the lighter shades), and directs vary 
considerably. 

2. Fastness to dilute Acids and Perspiration. Steep in cold 25 per 
cent. solution of acetic acid for five minutes. Wring, wash, and dry. 

3. Fastness to Washing. This test can be made in two ways :— 

(a) Steep for five minutes in a 1 per cent. solution of sodium 
carbonate. 
(6) Plait with a few threads of undyed yarn and boil for ten 
minutes in a 1 per cent. soap solution. If the colour 
“‘ bleeds,” the undyed yarn will be tinted, and it should 
also be filed in the record. 
15 


226 TEXTILE CHEMISTRY 


SPECIMEN PAGE oF RECORD 


Name of Colour used \.......00:00s00050cc00s504¢s00use9 skeen ean 
Class of Dye: Substantive or Direct Cotton Colour................... 
Shade Light Medium Dark Exhaust 


Percentage Dye used . . —- —_—— ioe Be kad 

Percentage Glauber or Salt — — eaeeeoner eee 

Percentage Soda Ash . . — —— ieee ened 
Samples of above, showing fastness to :— 


LLAGIA 2 Fee lite ney O O 


. Dil. Acids O O 
. Washing . Boe O O 
1 Sirippiig sae. oe sa O O 

io. O O 


. Bleaching 


ao -~» WwW bd 


Beamer ks ...ccsccoccccccsscucecsanecsceaccesdeees suncecouyeceneanaelne: tn =aa= === 


4. Fastness to ‘‘ Stripping.” Plait with white yarn and boil in 
pure water for fifteen minutes. Look for (a) tinting of white yarn ; 
(5) coloration of water ; (c) loss of colour on the dyed yarn. 

5. Fastness to Bleaching. There is considerable misconception 
with respect to what is known as “ fastness to bleaching ” and “ bleach- 
ing colours.” Almost any colour can be wholly or partly bleached if 
the bleaching process be intense enough. Modern laundries as a rule 
use bleaching chemicals in a manner which acts much more drastically 
than is the case in ordinary calico-bleaching, and it is unreasonable to 
ask for fastness to bleaching in an unlimited sense. 

The test here given is a reasonable one, and is similar to that applied 
by one of the largest manufacturers of “ cloths to stand bleaching * in 
Lancashire. 

Make a solution of fresh bleaching powder, strength 5 grams per 
100 c.c., and filter. 

Steen the dyed yarn in the (cold) filtrate for ten ativan’ 

Remove, and without squeezing or washing put it in dilute acetic 
acid or dilute sulphuric acid (1° Tw.) for ten minutes. 

Remove, wash well under running water, and dry in the air. 


SECTION XVIII 
MERCERIZING 


MERCERIZATION OR MERCERIZING OF COTTON 


This word was coined from the name of the discoverer of the 
phenomenon. 

John Mercer, whilst experimenting in 1860 with caustic soda solu- 
tion and cotton yarn, found that if the concentration reached about 
20 per cent.,and the fibre was steeped in it for 5 to 10 minutes, and 
afterwards removed and thoroughly washed, certain very noticeable 
changes had been produced :— 

1. There was a shrinkage in length, varying between } and } of 
the original. 

2. If the cotton was dried the weight was greater than that of the 
original by approximately 5 per cent. 

3. The strength of the yarn was also increased by anything up 
to 60 per cent. 

4. The fibre was made “ fuller.” 

5. It showed an increased affinity for dyes. 

This effect was not confined to cotton in the form of yarn—similar 
results could be produced in cloth. 

Mercer patented his process with the idea of putting on the market 
a stronger and fuller yarn and cloth. 

Unfortunately mercerized cotton was not a commercial success in 
Mercer’s lifetime, and in fact made very little progress until another 
property regarding it was discovered some thirty years later. Since 
then it has increased enormously in popularity. 

This important characteristic is produced by stretching the cotton 
during or after immersion in the alkali, and keeping it so during the 
washing process. | 

The fibre is thus prevented from contracting, with the result that an 
external lustre is produced. 

It is true that the increase in strength is reduced—being less than 
40 per cent. instead of 60 per cent., but the “silky ” effect obtained 
more than counterbalances this deficiency. 

The chemistry of the process as worked out by Gladstone is :— 

While the cotton is immersed in the soda solution a compound of 
cellulose and sodium oxide is formed. 

15* 


228 TEXTILE CHEMISTRY 


During the washing this is decomposed by the removal of the 
sodium and the substitution of hydrogen (from the water) in its place. 
This results in the production of a hydrate of cellulose. 

Assuming the empirical formula of cellulose to be (Cg5H1.0;5). we 
can represent the changes as follows :— 


(C,.H1,05)2 + 2Na0H — (C,H,.0;).Na.O + H,O. 
(C,H,,0;),Na,0 + 2H,0 = (C,H,,0;)..H,0 + 2NaOH. 


Mercerized cotton. 


The examination of mercerized cotton under the microscope shows 
that the fibre has been somewhat untwisted, the walls being con- 
siderably increased in thickness, the hollow flattened ribbon being 
changed to a thickened cylinder with practically no hollows (Fig. 240). 

Poor-quality or short-staple cotton is not suitable for mercer- 

izing, and the best results are obtained by using 2-fold 
- Egyption or Sea Island which has been previously 


| bleached. 
| The strength of caustic soda used should be between 
50°-70° Tw. and the operation should be conducted at 
a temperature of 60° Fah. After washing with water 
the lustre may be increased by washing with dilute 
acetic acid and the silky effect may be still further in- 
(@) creased by a special calendering process. 
The best chemical test to apply to yarn or cloth to 
_ detect mercerization is to treat the cotton with a cold 
: saturated solution of zine chloride, potassium iodide, 
Fi Ug. 240 and iodine. | 
The reagent is prepared by dissolving 
30 grams zinc chloride (pure solid) 
hog’, potassium iodide lin 24 c.c. of water. 
1 gram _ iodine 

It should be kept in a small glass stoppered bottle. . 

If the sample is white it may be used without previous preparation. 

If it is coloured it must be first bleached and dried before the test 
is applied. 

A very small piece (if cloth) or a few strands (if yarn) are im- 
mersed in the dry condition for 2 or 3 minutes in the liquid, and then 
transferred by means of a glass rod to an evaporating dish nearly full 
of water. By means of the rod the cotton is kept under the surface of 
the water and moved about to wash it. 

If the cotton has not been mercerized the dark blue colour will 
gradually become fainter and ultimately disappear. In the case of 
mercerized cotton the colour remains a distinct blue. | 


INDEX 


Acrtic acid, preparation and pro- 
perties of, 121, 122 

Acetylene, 117 

Acids, definitions and preparation of, 
66 


— reactions for detection of, 156, 157 
Action of chemicals on fibres, 162 

— heat on fibres, 162, 163 

Adhesives used in sizing, 174 
Adulterations in flour, 189 

Alcohol as a solvent, 20 

Alcohols, 118 

Aldehydes, 120 

Alkalis, definition and preparation of, 


66 

Alkali waste, 147 

Allotropic forms of sulphur, 148 

Alloys, 34 

Alum, properties of, 36, 139-142 

— solubility of, 142 

— — uses of, 140 

Alumina, 140 

Aluminium, preparation and _pro- 
perties of, 36 

— bronze, 140 

— chief compounds of, 140-142 

— determination of equivalent of, 93 

— sulphate, 142 

Ammonium chloride, 36 

— — crystals, '24 

— hydrate, preparation and properties 
of, 78 

— — use in dyeing, 79 

Amy] alcohol, 118 

Analysis of a simple salt, 154-157 

— air, 54, 55 

— — accurate method, 54 

— water, 43 

Animal charcoal, 102 

Anthracene, 116 

Antiseptics, definition of, 201, 174 

— examples of, 201 

Apparatus for preparation of pure 
water, 42 

Artificial silk, 161 

Ash in cotton, 165 

— — oils, 178 

— — silk, 167 

— — wool, 166 


» British thermal unit, 169 
, Bzrodlie’s apparatus estimation Ozdne;”’ ; °;’ ° 


229 , > 9 9 @ Pea? 2 g9 2B > > 
, > @3 90993 > 23 999 9999 


Aspirator, 4 
Atmosphere, The, 52-60 
Atomic theory, 80 

— weights, 81 

Atoms, 80 

Avogadro’s law, 89 


~ BacteriA, collection of, 60 


Balance for weighing, 8 

Bases, 66, 67 

Basic alum, 142 

— reactions, 153-155 

Beaker, 3 

Beaume’s scale, 14 

Belgian process for zinc, 143 

Bell jar, 4 

Bending glass tubing, 15 

Benzene, 21, 115, 116 

Black’s researches on chalk, 110 

Bleaching agents, 207 

— powder, preparation, properties, 
etc., and use of, 37, 127, 128, 131, 
209 

— with chlorine, 126, 127, 207, 205, 
213 

— — sulphur dioxide, 207 

Boiler feed water, 174 

— — — compositions for, 174, 175 

Boiling and evaporating compared, 27 

— point, apparatus for determination 
of, 27, 28 

— process of, 27 

Borax beads, 154 

Borda’s method of weighing, 11 

BO.Va 71 

Bowking, 209 

Boyle’s experiments with air, 53 

— law, 51 

Bradford conditioning house standard, 
166 

Breathing, 64 

— volume of air required for, 65 


¥9°? 


> "9 4 
a 
o > ? pf 9 > @ 


SCevecee 
© 


2 
. 3@ 29429009 ) a) 


Bunsen burner, 6 
— — method of using, 11, 12 
Burette,.5> 35° a 20) 9992 


"a" @ 2 


; ) 
2 9a > » Sa 
a , > 99d , ,a~o 

> 


ec « ‘China:clay; 146 $5 fet 8 ts ee 


230 


Burnett’s disinfecting fluid, 202 
Burnt alum, 142 
Butyric acid, 121 


CAKE alum, 142 

Calcium chloride in sizing, 200 

Calx, 53 

Cane sugar, 123 

Carbolic acid, 202 

Carbohydrates, 122-124 

Carbon-amorphous, 101 

— and its compounds, 101-124 

— properties of, 35 

Carbonates, analysis of by acid, 106— 
109 


— — heat, 109 

— tests for, 106 

Carbon dioxide, Angus Smith test for, 
57 

— — — — table, 58 

— — estimation of, 106-109 

— — inair, 57 

— — Pettenkofer test, 57-59 

— — preparation and properties of, 
103-105 

— — uses for, 105 

Carbon disulphide as a solvent, 20 

Carbonization of cotton, 140 

Carbon monoxide, preparation and 
properties of, 112, 114 

Carboy, 30 

Carded cotton, 164 

Carnallite, 144 

Cassava starch, 188 

— — microscopic-appearance of, 185 

Castner’s process, 129, 130 

Catalyst, 70 

Caustic soda, properties of, 37 

Cellulose, 123 

— in cotton fibre, 164 

Centigrade degrees, 12 

Cetyl alcohol, 118 

Charcoal, 102 

— reactions, 154 

Charles’ law, 49, 50 

— — determination of, 50 

Chemical arithmetic, examples in, 99 

— change, definition and examples of, 
37-39 

— — identification of, 38 

— tests for identification of fibres, 163 

— tools, 8-14 

— theory, 80-100 

Chemicking, 208 

— machine for, 210 ‘ 


Ce eee BS — £ < “ < j 
‘ i oo % 6% ying Keres eo” « ® cn @ 
~— ‘ignition of, 33 

— — in sizing, 196, 197 oe 

(— .- moissure im, LOT oe ose 
€éte“e © GEE « a & eeu ee ‘ 


€é 6 ¢ 


TEXTILE CHEMISTRY 


Chloroform as a solvent, 20 

— preparation and properties of, 117 

Chloros, 131 

Chlorine, plant for preparation of, 128, 
129 


— preparation and _ properties of, 
125, 131 

— uses for, 127 

Chrome, orange, 224 

— yellow, 224 

Clarke’s process for water softening, 41 

Classification of matter, 34, 35 

Coal, 102, 103 

— analysis of, 168-172 

— ash in, 168, 169 

— calorific value of, 169-172 

— determination of moisture in, 168 

— gas, 103 

— — waste, 148 

— tar, 103 

— — asa source of ammonia, 78 

Cocoa-nut oil soap, 193 

Coke, 102 

Colour, nature of, 205 

Condensed water, 174 

Cold saturated solution, preparation 
of, 23, 24 

Combustion, Lavoisier’s theory of, 64 

— process of, 64 

Composite nature of white light, 205, 
206 

Composition of cotton fibres, 163, 164 

— — raw wool, 166 

— — water, 45 

Compounds, definition of, 34 

— examples of, 35 

Conditioning of cotton, 164 

— — wool, 166 

Constitution of air, 55 

Cooper’s viscometer, 181, 182 

Copper, determination of equivalent of, 
93 


— properties of, 35 

— oxide, properties of, 35 

— sulphate, 202, 36 

Cork boring, 16 

Correction of volume of gas to N.T.P., 


Cotton fibres, diagrams of, 161 
Crucible, 6 

Cryolite, 140 

Crystallization, 22, 24 
Crystals, 22 


- Deacon process for chlorine, 129 
: Degree of solubility, determination of, 
4 


Detection of acidic radicles, 156, 157 
— — chlorides in cotton, 164, 165 
— — metallic radicles, 152-155 


INDEX 


Detergents, 207 

Determination of ash in cotton, 165 
— — — — substances, 32, 33 
— — moisture in cotton, 165 
Dextrine, properties of, 37 
Dextrose, 126 

Diagrams, 1-7 

Diffusion of gases, 51 

Direct dyes, 215, 216 
Distillation, apparatus for, 21 

— process of, 21 

— flask, 7 

— water, apparatus for, 21 
Distilled water, apparatus for, 21 
— — preparation of, 21 
Dolomite, 144 

D.O.V., 71 

Drawing of diagrams, 1-7 
Drawn silver, 164 

Drying tower, 7 

Dust in air, 59, 60 

Dyeing cotton with basics, 216, 217 
— — — directs, 215, 216 

— — — minerals, 223, 224 

— — — sulphurs, 222, 223 
Dyeing, processes of, 214-226 


Eau de Javelle, 130 

— — Labaraque, 130 

Effect of solution on weight, 23 

Effects of heat, examples of, 31 

— — — on substances, 31 

Electric bleach, 209, 210 

Electrolytic decomposition water, 45 

— — — apparatus for, 45 

Elements, definition of, 34 

— examples of, 34 

Epsom salts, 144 

Equations, list of, 98, 99 

— meaning of, 97 

— use of, 97 

Equivalents, definition of, 89 

— determination of, 89-94 

— — — by precipitation, 93 

— table of values for, 94 

Estimation of iron in water, 174 

Ether as a solvent, 20 

Ethers, preparation and properties of, 
119 

Ethyl alcohol, 118 

— ether, 119 

Ethylene, 117 

Evaporation, process of, 23 

Exercises in solution, 22 

— — use of balance, 10 

Exercises with Joly balance, 11 

Experimental dyeing “‘ Directs,’ 219, 
220 

Experiments with starch, 188, 189 

Eyepiece, 159 


231 


FAHRENHEIT degrees, 12 

Farina, microscopic appearance, 185 

— preparation and properties, 186, 187 

Fastness to acids, 225 

— — bleaching, 226 

— — light, 225 

— — perspiration, 225 

— — stripping, 226 

— — washing, 225 

Fatty acids, 121 

Fatty oils used for textile purposes, 176 

Feeding, 221 

Fermentation, 200, 201 

Ferments, 200 

Ferrous suphate, properties of, 36 

Fibres, microscopic appearance, 161 

Filtration, process of, 25, 27 

Filtering media, 27 

Fitting up apparatus, 18, 19 

Fixing, 217 

Flame reactions, 154 

Flash point apparatus, 178 

Flask, 1 

Flour, 37 

— ash in, 184 

— moisture in, 184 

— preparation and properties of, 184— 
186 


— starch in, 184 

Flue gases, examination of, 172-174 

Formaldehyde, preparation and pro- 
perties of, 120 

Formalin, preparation and properties 
of, 12 

— asan antiseptic, 202 

Formic acid, 121, 122 

Formuls, list of, 96, 97 

— meaning of, 96 

Free acid in oils, determination of, 178 

— alkalis in oils, 178 

— fatty acid in oils, determination of, 
182 

Fresh air, 53 


GALVANIZED iron, 142 

Gas carbon, 102 

Gases, 34 

— apparatus for solubility of, 20 
— classification of, 47 

— collection of, 49 

— determination of density of, 47 
— general properties of, 47-52 
— relative densities of, 47 . 

— solubility of, 20, 47 

— table of properties of, 47 

Gas jar, 3 

— liquor, 78 

Generator gas, 112 

Germs in air, 60 . 


232 


Glass bends, 2, 3, 15, 16 

— bulbs, making of, 16 

— jets, making of, 16 

— manipulation, 15-17 

— tubing, 3 

Glucose, properties of, 36, 123 

Gluten, estimation of, 186, 189 

— in flour, test for, 186 

Glycerides, 68 

Glycerine as an antiseptic, 202 

— preparation and properties of, 194, 
195 

— tests for, 195 

Graham’s law, 52 

Grape sugar, 123 

Graphite, 101 

Gun cotton, 75 


HARDNESS of water, 41 

— definition of, 43 

— permanent, 43 

— temporary, 43 

Hard water, 41 

Heating glass tubing, 15 

Homologous series, 115 

Honey, 123 

Hooke’s law, 11 

Houzeau’s test, 137 

Humidity, 55-57 

— Home Office regulations, 57 

— in mills, 57 

— table, 56 

Hydrocarbons, preparation and pro- 
perties of, 114-117 

Hydrochloric acid, electrolysis of, 126 

— — plant for manufacture, 77 

— — preparation and properties of, 

— — uses, 77 

Hydrogen peroxide, estimation of, 135 

— — preparation and properties of, 
133-135 

— sulphide, preparation and _ pro- 
perties of, 149-152 

Hydrometers, 12, 13 

— use of, 29 

Hypochlorites, preparation and pro- 
perties of, 130 

Hypochlorous acid, 130 


IDENTIFICATION of common substances, 
35-37 

— — gases, tests for, 52 

Impurities in cotton fibre, 164 

Indicators, 67 

Instruction for dyeing basic colours, 
221 

Invert sugar, 124 

Iodoform, 202 

Iron buff, 224 


TEXTILE CHEMISTRY 


Iron, equivalent of, 92 
— properties of, 36 


JouLy balance, 11 


Kaotrn, 140 
Kiers, 208, 209 
Kieserite, 208, 209 


LABORATORY experiments with clay, 
197, 198 

— still, 21 

Lactose, 123, 124 

Lakes, formation of, 142 

Lampblack, 102 

Lanoline, 196 

Lavoisier’s apparatus, 54 

— experiments with air, 53 

Law of constant proportion, 82 

— — gaseous volumes, 85 

— — multiple proportion, 82 

— — reciprocal proportion, 83 

Laws of Chemical combination, 82-89 

— — — — experiments to illustrate, 
83-85 

Lavozone, 131 

Lead peroxide, properties of, 36 

— properties of, 36 

— plaster, 68 

Levulose, 123 

Lewis Thompson calorimeter, 171, 172 

Liebig condenser, 6, 21 

Linen, microscopic appearance, 161 

Liquids, 34 

Liquid sulphur dioxide, 133 


Maenatium, 140 

Magnesite. 144 

Magnesium, determination of equiva- 
lent of, 91 

— preparation and properties of, 36, 
144, 145 

— carbonate, preparation and pro- 
perties of, 147 

— — decomposition of, 146 

— chloride in sizing, 199-200 

— — preparation and properties of, 
145, 199 

— oxide, 146 ¢ 

— sulphate, preparation and pro- 
perties of, 146, 147 

Magnifying power, 159 

Maize starch, microscopic appearance, 
185 

—  — preparation and properties of, 
187, 188 | 

Maltose, 124 

Manganese bronze, 225 

— dioxide, properties of, 35 

Manometer, 51 


° 


INDEX 


Manipulation during dyeing, 216 

Marble, properties of, 36 

Marsh gas, preparation and properties, 
114 


Mass of 1 litre of hydrogen, determina- 
tion of, 90 

Mather and Platt electrolyzer, 212 

Melting point apparatus, 17 

— — determination of, 27, 28 

Mercerized cotton under microscope, 
228 

Mercerizing, process of, 227 

Mercerization, test for, 228 

Mercuric chloride as an antiseptic, 202 

— oxide, properties of, 36 

Metals, examples of, 34 

— properties of, 34 

Metallic chlorides in sizing, 198 

Methane, preparation and properties 
of, 114 

Methyl alcohol, 118 

— ether, 119 

— group, 115 

Microscope, construction and use of, 
158-160 

Microscopic appearance of starches, 185 

Mildew, 201 

Milk sugar, 123, 124 

Milligram weights, 10 

Milton, 131, 213 

Mineral oils, 176, 177 

Mixtures and pure substances com- 
pared, 35 

— definition of, 35 

— examples of, 35 

Moisture in air, 55 

— — cotton fibre, 164 

— — wool fibre, 166 

Molecular weights, 81 

Molecules, 80, 81 

Mordanting, 217 

Mordants, aluminium, 142 

— for basic dyes, 217 

Mule spun yarn, 164 

Mycoderma aceti, 201 


NAPHTHALENE, 116 

Native sulphur, 147 

Natural fibres, 158-167 

Neutralization, 67 

Newtonian experiment on white light, 
205 

Nitrate of iron, 224 

Nitre cake, 73 

— crystals, 24 

Nitric acid, experiments to illustrate 
properties of, 74, 75 

— — from nitre, 72 

— — percentage composition of, 71 

— — plant, 72 


233 


Nitric Acid, preparation and properties 
of, 71-75 

— — uses for, 75 

Nitrobenzene, 75 

Norwegian nitre, 73 


OBJECTIVE, 159 

Oetell electrolyzer, 210, 211 

Oil of vitriol, 68 

Oils, classification of, 175 

— ether, extraction of, 176 

— examination of, 177-182 

— expressing, 175 

— preparation and properties of, 175- 
182 


— rendering, 175 

Oleates, 68 

Oleic acid, preparation and properties 
of, 121 

Oxalic acid, preparation and _pro- 
perties of, 121 

Oxidation, 63 

Oxides, 63, 65 

— acidic, 65 

— basic, 65 

— classification of, 65 

— examples of, 65 

— insoluble, 65 

— soluble in nitric acid, 65 

— — water, 65 

Sane or agents, 63 

Oxygen, estimation of volume of, 62, 63 

— from bleaching powder, 62 

— — liquid air, 62 

— — mercuric oxide, 61 

— — potassium chlorate, 61 

— — potassium permanganate, 62 

— preparation, apparatus used for, 61, 
62 


— — and properties, 61-65 

Ozone, estimation of, 138 

— experiments with, 137, 138 

— Houzeau’s test, 137 

— Ostwald’s apparatus, 136 

— preparation and properties, 136-138 
— tube, 136 


PAETCHNER’S solution, 131 

Palmitates, 68 

Palmitic acid, properties of, 121 

Papin digester, 28 

Paraffin wax, 115 

Parozone, 131 

Pasteur’s experiments, 200, 201 

Patent alum, 142 

Percentage of water, determination of, 
31, 32 

Peroxides, 65 

Petroleum, 115 

— oil, fractions from, 177 


234 


Phenol, 118, 119 

Phosgene gas, 114 

Phosphates, 68 

— in tallow, test for, 192 

Physical change, definition and exam- 
ples of, 37-39 

Picric acid, 75, 119 

Pipette, 5 

Pneumatic trough, 6 

Potash bulb, 8 

Potassium chlorate, properties of, 36 

— nitrate, properties of, 36 

Precipitates and their nature, 27 

Preliminary tests in analysis, 154 

Preparation of gases, general methods 
for, 48, 49 

—  — sodium hypochlorite by elec- 
trolysis, 210-212 

Preservatives in size, 203 

Pressure gauge, 51 

Principle of the hydrometer, 13 

Principles of analysis, 152-154 

Process of weighing, 10 

Producer gas, 112 

Production of colour, 206 

Properties of cotton fibre, 163-165 

— — wool fibre, 165, 166 

Prussian blue, 225 

Pure hard soap, 193 

— water, preparation of, 41 

— — properties of, 41, 42 


Ratz of filtration, factors governing, 27 

Raw cotton, 163 

Recovered grease, 196 

Red lead, 36 

— liquor, 141 

Redwood viscometer, 179 

Refraction of light, 205 

Relation °F. to ° C., 13 

— sp. gr. to ° Tw., 13 

Relative humidity, determination of, 
55, 56 

Rendering of tallow, 190 

Residues and ashes, examination of, 
203, 204 

Retort, 1 

— stand, 6 

Rhombic sulphur, 148, 149 

Rice starch, 188 

— — microscopic appearance of, 185 

Rider, 10 

Rock oil, 177 

Roland Wild calorimeter, 170 

Roving, 164 


Saao, microscopic appearance of, 185 
— preparation and properties of, 187 
Sal-ammoniac, 78 
— — crystals, 24 


TEXTILE CHEMISTRY 


Salicylic acid as an antiseptic, 203 

Salt, properties of, 36 

Salts, examples of, 67 

— preparation and properties of, 66, 67 

Saponification, 68 

Saturated solution, 21, 22 

Schiff’s reagent, 120 

Scotch shale oils, 177 

Scutched cotton, 164 

Sea water, constitution of, 41 

Separation, Soluble and insoluble sub- 
stances, 25, 26 

Shower proofing, 141 

Siemens ozone tube, 136 

Silesian process (zinc), 143 

Silk, composition of, 167 

— microscopic appearance, 161 

— properties of, 166, 167 

Simple viscometer, 180 

Singeing machine, 208 

— process, 208 

Sizing ingredients, classification of, 184 

— of cotton yarn, 183-204 

Smoothing glass tubing, 16 

Soap, preparation and properties, 192- 
194 


Sodium carbonate, properties of, 37 

Sodium hypochlorite, 131 

Softeners used in sizing, 174 

Softening of water, 41 

Solids, 34 

Solution, process of, 20, 22 

Solubility of ammonia in water, 79 

— — apparatus, 18, 19 

— gases, determination of, 47 

— solids in water, 22 

— tallow, 191 

Solvents, 20 

Souring, 208, 210 

Specific gravity bottle, 29 

— — definition of, 29 

— — determination of, 29 

— — liquids, 29 

— — oils, 177 

— — solids, 30 

— — waxes, 30 

Spelter, 143 

Spirits of hartshorn, 78 

Standard hard water, preparation of, 
44 

— soap solution, preparation of, 44 

— solutions, preparation of, 25 

Starch, properties of, 37 

Starches, 123, 124 

Stearic acid, properties of, 121 

Substances dissolved in natural waters, 
4] 

Substitution compounds, 117 

Sucroses, 123 

Sugar (cane), 36 


INDEX 


Sugars, 123 

Sulphates, 147 

Sulphides, 147 

Sulphur dioxide, preparation and pro- 
perties, 132, 133 

— — uses, 133 

Sulphites, 132 

Sulphuretted hydrogen, preparation 
and properties of, 149, 151 

— — reactions with, 150, 151 

Sulphuric acid, action of metals on, 71 

— — contact process, 70 

— — English process, 69, 70 

— — identification of, 71 

— — preparation and properties of, 
68-71 

— — Specific gravity of, 71 

— — strengths of, 71 

— — uses of, 71 

Sulphuric ether, 119 

Sulphur or sulphide colours, 222 

— — — properties of, 222 

— — — trade names for, 222 

— preparation and properties, 36, 
147-149 

Symbols, meaning of, 95, 96 

Symbols, table of, 96 

Synthesis of Water, 45, 46 

Systems of crystallography, 22 


TABLE of hardness, 44 

— — viscosities, 182 

Tallow, preparation and properties of, 
190-192 

Temperature of dye bath, 216 

Testing soap for ash, 194 

— — — free alkali, 194 

— — — water, 194 

— tallow, 192 

— zine chloride, 199 

Tests for pure water, 42 

Textile chemistry, definition of, 158 

Thermometers, 12 

Thistle funnel, 7 

Tinctures, 20 

T.N.1., 75 

Total solids in water, 43 

Tripod and gauze, 4 

Twaddell graduations, 13 

Tweezers, 9 

Two volume formula gases, 85-89 

Tyndall’s experiments, 201, 203 


Union cloth, microscopic appearance 
of, 161 7 

Unwashed wool, 166 

Use of soap in sizing, 194 

Uses for water, 46 


235 


VALENCY, graphic representation of, 
95 


— table of, 94 

— theory of, 94, 95 

Ventilation of buildings, 59 

— principles of, 59 

Viscosity of oils, determination of, 
179-182 

Volume and mass of gases, relation 
between, 99 

— of carbon dioxide, from carbonates, 
111 

— — dye bath, 215 

Volumetric composition of ammonia, 
87, 88 

— — — carbon dioxide, 88 

— — — gases, 85-89 

— — — hydrogen chloride, 86, 87 

— — — — sulphide, 89 

—- —— —=+ pitric oxide, 89 

— — — nitrous oxide, 89 

— — — steam, 85, 86 

— — — sulphur dioxide, 88 


Wasu bottle, 17 
Washed wool, 166 
Washing machine, 210 
Water, dissolved solid in, 41 
— gas, 112 
— in tallow, 191 
— rain, 40 
— — gases in, 40 
— softening plant, principle of, 44, 45 
— sources of, 40 
— suspended solids in, 40, 41 
axes used in sizing, 195, 196 
Weighing bottles, 32 
Weighting materials in sizing, 174 
Weights for use with balance, 9 
Weldon mud, 129 
— recovery process, 128 
Wet and dry bulb thermometer, 56 
Wheat starch, microscopic appearance 
of, 185 
Wool grease, 196 
Wool, microscopic appearance of, 61 
Woulfe bottle, 4 


YORKSHIRE grease, 196 


Zino, chief compounds of, 143, 144 

— chloride, 143, 144, 198 

— equivalent, determination of, 92 

— oxide, 144 

— preparation and properties of, 36, 
142, 143 

sulphate, 144 

sulphide, 144 

chloride as an antiseptic, 202 

— impurities in, 198, 199 


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